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	$42.59	6.505%	$45.3605	$45.36	$45.35	$45.40
Purchase #2	$22.29	13.801%	$25.3662	$25.37	$25.35	$25.40
Purchase #3	$178.27	7.549%	$191.7276	$191.73	$191.75	$191.70
Purchase #4	$36.68	13.646%	$41.6854	$41.69	$41.70	$41.70
Purchase #5	$45.33	13.737%	$51.557	$51.56	$51.55	$51.60
Purchase #6	$36.77	9.383%	$40.2201	$40.22	$40.20	$40.20
Purchase #7	$207.47	12.556%	$233.5199	$233.52	$233.50	$233.50
7 purchase totals =	$569.40		$629.4367	$629.45	$629.40	$629.50