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	$99.75	12.154%	$111.8736	$111.87	$111.85	$111.90
Purchase #2	$158.41	4.225%	$165.1028	$165.10	$165.10	$165.10
Purchase #3	$20.96	9.297%	$22.9087	$22.91	$22.90	$22.90
Purchase #4	$238.75	8.846%	$259.8698	$259.87	$259.85	$259.90
Purchase #5	$157.78	7.328%	$169.3421	$169.34	$169.35	$169.30
Purchase #6	$145.84	5.353%	$153.6468	$153.65	$153.65	$153.60
Purchase #7	$156.69	12.114%	$175.6714	$175.67	$175.65	$175.70
7 purchase totals =	$978.18		$1,058.4152	$1,058.41	$1,058.35	$1,058.40