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	$143.65	7.556%	$154.5042	$154.50	$154.50	$154.50
Purchase #2	$79.68	13.753%	$90.6384	$90.64	$90.65	$90.60
Purchase #3	$150.37	13.839%	$171.1797	$171.18	$171.20	$171.20
Purchase #4	$90.41	12.346%	$101.572	$101.57	$101.55	$101.60
Purchase #5	$212.85	11.533%	$237.398	$237.40	$237.40	$237.40
Purchase #6	$192.34	9.137%	$209.9141	$209.91	$209.90	$209.90
Purchase #7	$163.92	13.434%	$185.941	$185.94	$185.95	$185.90
7 purchase totals =	$1,033.22		$1,151.1474	$1,151.14	$1,151.15	$1,151.10