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	$157.89	3.135%	$162.8399	$162.84	$162.85	$162.80
Purchase #2	$151.59	7.745%	$163.3306	$163.33	$163.35	$163.30
Purchase #3	$53.67	9.707%	$58.8797	$58.88	$58.90	$58.90
Purchase #4	$92.81	8.188%	$100.4093	$100.41	$100.40	$100.40
Purchase #5	$172.76	8.159%	$186.8555	$186.86	$186.85	$186.90
Purchase #6	$82.30	8.820%	$89.5589	$89.56	$89.55	$89.60
Purchase #7	$147.81	5.126%	$155.3867	$155.39	$155.40	$155.40
7 purchase totals =	$858.83		$917.2606	$917.27	$917.30	$917.30