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	$144.89	5.468%	$152.8126	$152.81	$152.80	$152.80
Purchase #2	$153.72	7.524%	$165.2859	$165.29	$165.30	$165.30
Purchase #3	$250.55	6.694%	$267.3218	$267.32	$267.30	$267.30
Purchase #4	$56.72	3.812%	$58.8822	$58.88	$58.90	$58.90
Purchase #5	$63.95	10.664%	$70.7696	$70.77	$70.75	$70.80
Purchase #6	$147.65	4.834%	$154.7874	$154.79	$154.80	$154.80
Purchase #7	$200.87	7.221%	$215.3748	$215.37	$215.35	$215.40
7 purchase totals =	$1,018.35		$1,085.2343	$1,085.23	$1,085.20	$1,085.30