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	$182.74	4.460%	$190.8902	$190.89	$190.90	$190.90
Purchase #2	$19.63	3.263%	$20.2705	$20.27	$20.25	$20.30
Purchase #3	$94.91	11.770%	$106.0809	$106.08	$106.10	$106.10
Purchase #4	$79.99	6.483%	$85.1758	$85.18	$85.20	$85.20
Purchase #5	$162.32	13.635%	$184.4523	$184.45	$184.45	$184.50
Purchase #6	$231.96	5.126%	$243.8503	$243.85	$243.85	$243.90
Purchase #7	$59.30	3.840%	$61.5771	$61.58	$61.60	$61.60
7 purchase totals =	$830.85		$892.2971	$892.30	$892.35	$892.50