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	$162.77	3.484%	$168.4409	$168.44	$168.45	$168.40
Purchase #2	$83.49	8.788%	$90.8271	$90.83	$90.85	$90.80
Purchase #3	$24.92	6.349%	$26.5022	$26.50	$26.50	$26.50
Purchase #4	$227.59	6.581%	$242.5677	$242.57	$242.55	$242.60
Purchase #5	$171.60	11.740%	$191.7458	$191.75	$191.75	$191.70
Purchase #6	$39.47	4.793%	$41.3618	$41.36	$41.35	$41.40
Purchase #7	$149.31	7.187%	$160.0409	$160.04	$160.05	$160.00
7 purchase totals =	$859.15		$921.4864	$921.49	$921.50	$921.40