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	$111.56	12.825%	$125.8676	$125.87	$125.85	$125.90
Purchase #2	$217.41	8.627%	$236.166	$236.17	$236.15	$236.20
Purchase #3	$150.63	3.216%	$155.4743	$155.47	$155.45	$155.50
Purchase #4	$76.28	6.744%	$81.4243	$81.42	$81.40	$81.40
Purchase #5	$174.87	3.818%	$181.5465	$181.55	$181.55	$181.50
Purchase #6	$166.52	11.443%	$185.5749	$185.57	$185.55	$185.60
Purchase #7	$66.99	8.282%	$72.5381	$72.54	$72.55	$72.50
7 purchase totals =	$964.26		$1,038.5917	$1,038.59	$1,038.50	$1,038.60