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	$137.68	10.460%	$152.0813	$152.08	$152.10	$152.10
Purchase #2	$201.76	10.155%	$222.2487	$222.25	$222.25	$222.20
Purchase #3	$154.49	7.695%	$166.378	$166.38	$166.40	$166.40
Purchase #4	$203.98	12.478%	$229.4326	$229.43	$229.45	$229.40
Purchase #5	$98.59	11.629%	$110.055	$110.06	$110.05	$110.10
Purchase #6	$170.33	12.419%	$191.4833	$191.48	$191.50	$191.50
Purchase #7	$193.88	11.715%	$216.593	$216.59	$216.60	$216.60
7 purchase totals =	$1,160.71		$1,288.2719	$1,288.27	$1,288.35	$1,288.30