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	$144.81	4.609%	$151.4843	$151.48	$151.50	$151.50
Purchase #2	$121.98	4.572%	$127.5569	$127.56	$127.55	$127.60
Purchase #3	$202.91	4.805%	$212.6598	$212.66	$212.65	$212.70
Purchase #4	$105.82	3.172%	$109.1766	$109.18	$109.20	$109.20
Purchase #5	$187.56	7.548%	$201.717	$201.72	$201.70	$201.70
Purchase #6	$30.64	5.846%	$32.4312	$32.43	$32.45	$32.40
Purchase #7	$60.54	6.556%	$64.509	$64.51	$64.50	$64.50
7 purchase totals =	$854.26		$899.5348	$899.54	$899.55	$899.60