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	$152.28	12.131%	$170.7531	$170.75	$170.75	$170.80
Purchase #2	$134.68	9.405%	$147.3467	$147.35	$147.35	$147.30
Purchase #3	$56.70	9.249%	$61.9442	$61.94	$61.95	$61.90
Purchase #4	$139.36	9.162%	$152.1282	$152.13	$152.15	$152.10
Purchase #5	$172.70	4.354%	$180.2194	$180.22	$180.20	$180.20
Purchase #6	$229.43	9.351%	$250.884	$250.88	$250.90	$250.90
Purchase #7	$172.45	9.200%	$188.3154	$188.32	$188.30	$188.30
7 purchase totals =	$1,057.60		$1,151.5910	$1,151.59	$1,151.60	$1,151.50