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	$147.29	12.842%	$166.205	$166.21	$166.20	$166.20
Purchase #2	$188.31	3.416%	$194.7427	$194.74	$194.75	$194.70
Purchase #3	$250.29	6.744%	$267.1696	$267.17	$267.15	$267.20
Purchase #4	$39.51	10.346%	$43.5977	$43.60	$43.60	$43.60
Purchase #5	$235.75	4.614%	$246.6275	$246.63	$246.65	$246.60
Purchase #6	$154.83	13.118%	$175.1406	$175.14	$175.15	$175.10
Purchase #7	$55.29	7.540%	$59.4589	$59.46	$59.45	$59.50
7 purchase totals =	$1,071.27		$1,152.9420	$1,152.95	$1,152.95	$1,152.90