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	$132.33	6.370%	$140.7594	$140.76	$140.75	$140.80
Purchase #2	$164.48	6.663%	$175.4393	$175.44	$175.45	$175.40
Purchase #3	$14.81	13.857%	$16.8622	$16.86	$16.85	$16.90
Purchase #4	$59.67	3.673%	$61.8617	$61.86	$61.85	$61.90
Purchase #5	$85.39	12.855%	$96.3669	$96.37	$96.35	$96.40
Purchase #6	$30.48	11.213%	$33.8977	$33.90	$33.90	$33.90
Purchase #7	$76.97	11.145%	$85.5483	$85.55	$85.55	$85.50
7 purchase totals =	$564.13		$610.7355	$610.74	$610.70	$610.80