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	$86.28	6.122%	$91.5621	$91.56	$91.55	$91.60
Purchase #2	$141.65	6.450%	$150.7864	$150.79	$150.80	$150.80
Purchase #3	$56.90	13.871%	$64.7926	$64.79	$64.80	$64.80
Purchase #4	$238.52	7.292%	$255.9129	$255.91	$255.90	$255.90
Purchase #5	$18.85	9.695%	$20.6775	$20.68	$20.70	$20.70
Purchase #6	$243.26	13.760%	$276.7326	$276.73	$276.75	$276.70
Purchase #7	$196.27	6.151%	$208.3426	$208.34	$208.35	$208.30
7 purchase totals =	$981.73		$1,068.8067	$1,068.80	$1,068.85	$1,068.80