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	$203.40	10.288%	$224.3258	$224.33	$224.35	$224.30
Purchase #2	$221.85	6.568%	$236.4211	$236.42	$236.40	$236.40
Purchase #3	$164.92	4.722%	$172.7075	$172.71	$172.70	$172.70
Purchase #4	$65.39	9.793%	$71.7936	$71.79	$71.80	$71.80
Purchase #5	$167.59	13.540%	$190.2817	$190.28	$190.30	$190.30
Purchase #6	$194.52	7.634%	$209.3697	$209.37	$209.35	$209.40
Purchase #7	$221.39	13.210%	$250.6356	$250.64	$250.65	$250.60
7 purchase totals =	$1,239.06		$1,355.5350	$1,355.54	$1,355.55	$1,355.50