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	$151.75	7.338%	$162.8854	$162.89	$162.90	$162.90
Purchase #2	$228.87	10.558%	$253.0341	$253.03	$253.05	$253.00
Purchase #3	$144.26	11.260%	$160.5037	$160.50	$160.50	$160.50
Purchase #4	$102.90	3.156%	$106.1475	$106.15	$106.15	$106.10
Purchase #5	$223.28	11.105%	$248.0752	$248.08	$248.10	$248.10
Purchase #6	$94.54	11.872%	$105.7638	$105.76	$105.75	$105.80
Purchase #7	$22.58	11.705%	$25.223	$25.22	$25.20	$25.20
7 purchase totals =	$968.18		$1,061.6327	$1,061.63	$1,061.65	$1,061.60