Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.87	6.868%	$151.6136	$151.61	$151.60	$151.60
Purchase #2	$173.54	6.289%	$184.4539	$184.45	$184.45	$184.50
Purchase #3	$176.89	11.287%	$196.8556	$196.86	$196.85	$196.90
Purchase #4	$190.71	4.155%	$198.634	$198.63	$198.65	$198.60
Purchase #5	$170.39	9.458%	$186.5055	$186.51	$186.50	$186.50
Purchase #6	$172.95	10.121%	$190.4543	$190.45	$190.45	$190.50
Purchase #7	$178.59	13.291%	$202.3264	$202.33	$202.35	$202.30
7 purchase totals =	$1,204.94		$1,310.8433	$1,310.84	$1,310.85	$1,310.90