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	$167.45	5.792%	$177.1487	$177.15	$177.15	$177.10
Purchase #2	$118.25	11.240%	$131.5413	$131.54	$131.55	$131.50
Purchase #3	$191.40	7.151%	$205.087	$205.09	$205.10	$205.10
Purchase #4	$134.98	12.297%	$151.5785	$151.58	$151.60	$151.60
Purchase #5	$245.30	7.261%	$263.1112	$263.11	$263.10	$263.10
Purchase #6	$219.43	4.511%	$229.3285	$229.33	$229.35	$229.30
Purchase #7	$166.74	3.471%	$172.5275	$172.53	$172.55	$172.50
7 purchase totals =	$1,243.55		$1,330.3227	$1,330.33	$1,330.40	$1,330.20