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	$110.67	13.345%	$125.4389	$125.44	$125.45	$125.40
Purchase #2	$82.60	3.279%	$85.3085	$85.31	$85.30	$85.30
Purchase #3	$146.46	5.389%	$154.3527	$154.35	$154.35	$154.40
Purchase #4	$132.94	11.671%	$148.4554	$148.46	$148.45	$148.50
Purchase #5	$207.70	7.740%	$223.776	$223.78	$223.80	$223.80
Purchase #6	$146.47	9.589%	$160.515	$160.52	$160.50	$160.50
Purchase #7	$180.53	5.861%	$191.1109	$191.11	$191.10	$191.10
7 purchase totals =	$1,007.37		$1,088.9574	$1,088.97	$1,088.95	$1,089.00