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	$131.46	9.773%	$144.3076	$144.31	$144.30	$144.30
Purchase #2	$100.28	6.459%	$106.7571	$106.76	$106.75	$106.80
Purchase #3	$94.98	11.334%	$105.745	$105.75	$105.75	$105.70
Purchase #4	$158.73	4.647%	$166.1062	$166.11	$166.10	$166.10
Purchase #5	$196.40	4.338%	$204.9198	$204.92	$204.90	$204.90
Purchase #6	$147.35	5.770%	$155.8521	$155.85	$155.85	$155.90
Purchase #7	$206.95	10.240%	$228.1417	$228.14	$228.15	$228.10
7 purchase totals =	$1,036.15		$1,111.8295	$1,111.84	$1,111.80	$1,111.80