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	$221.70	12.792%	$250.0599	$250.06	$250.05	$250.10
Purchase #2	$17.93	3.449%	$18.5484	$18.55	$18.55	$18.50
Purchase #3	$235.38	4.268%	$245.426	$245.43	$245.45	$245.40
Purchase #4	$6.99	4.870%	$7.3304	$7.33	$7.35	$7.30
Purchase #5	$193.45	3.360%	$199.9499	$199.95	$199.95	$199.90
Purchase #6	$224.72	9.154%	$245.2909	$245.29	$245.30	$245.30
Purchase #7	$51.40	3.692%	$53.2977	$53.30	$53.30	$53.30
7 purchase totals =	$951.57		$1,019.9032	$1,019.91	$1,019.95	$1,019.80