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	$130.59	10.351%	$144.1074	$144.11	$144.10	$144.10
Purchase #2	$73.34	13.594%	$83.3098	$83.31	$83.30	$83.30
Purchase #3	$6.63	10.855%	$7.3497	$7.35	$7.35	$7.30
Purchase #4	$139.83	4.197%	$145.6987	$145.70	$145.70	$145.70
Purchase #5	$148.64	10.556%	$164.3304	$164.33	$164.35	$164.30
Purchase #6	$45.27	12.369%	$50.8694	$50.87	$50.85	$50.90
Purchase #7	$112.73	13.319%	$127.7445	$127.74	$127.75	$127.70
7 purchase totals =	$657.03		$723.4099	$723.41	$723.40	$723.30