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	$167.43	7.285%	$179.6273	$179.63	$179.65	$179.60
Purchase #2	$234.26	10.285%	$258.3536	$258.35	$258.35	$258.40
Purchase #3	$175.45	9.391%	$191.9265	$191.93	$191.95	$191.90
Purchase #4	$44.59	13.139%	$50.4487	$50.45	$50.45	$50.40
Purchase #5	$74.47	8.303%	$80.6532	$80.65	$80.65	$80.70
Purchase #6	$148.82	11.656%	$166.1665	$166.17	$166.15	$166.20
Purchase #7	$200.52	10.289%	$221.1515	$221.15	$221.15	$221.20
7 purchase totals =	$1,045.54		$1,148.3273	$1,148.33	$1,148.35	$1,148.40