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	$220.54	9.513%	$241.52	$241.52	$241.50	$241.50
Purchase #2	$86.88	5.237%	$91.4299	$91.43	$91.45	$91.40
Purchase #3	$194.56	6.463%	$207.1344	$207.13	$207.15	$207.10
Purchase #4	$123.37	10.399%	$136.1992	$136.20	$136.20	$136.20
Purchase #5	$100.95	10.310%	$111.3579	$111.36	$111.35	$111.40
Purchase #6	$147.51	11.772%	$164.8749	$164.87	$164.85	$164.90
Purchase #7	$127.54	10.681%	$141.1625	$141.16	$141.15	$141.20
7 purchase totals =	$1,001.35		$1,093.6788	$1,093.67	$1,093.65	$1,093.70