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	$63.51	12.613%	$71.5205	$71.52	$71.50	$71.50
Purchase #2	$61.79	8.262%	$66.8951	$66.90	$66.90	$66.90
Purchase #3	$65.86	10.627%	$72.8589	$72.86	$72.85	$72.90
Purchase #4	$63.65	12.254%	$71.4497	$71.45	$71.45	$71.40
Purchase #5	$165.64	10.381%	$182.8351	$182.84	$182.85	$182.80
Purchase #6	$235.65	13.790%	$268.1461	$268.15	$268.15	$268.10
Purchase #7	$170.90	6.812%	$182.5417	$182.54	$182.55	$182.50
7 purchase totals =	$827.00		$916.2471	$916.26	$916.25	$916.10