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	$42.41	8.163%	$45.8719	$45.87	$45.85	$45.90
Purchase #2	$233.65	13.314%	$264.7582	$264.76	$264.75	$264.80
Purchase #3	$37.63	10.540%	$41.5962	$41.60	$41.60	$41.60
Purchase #4	$245.53	10.784%	$272.008	$272.01	$272.00	$272.00
Purchase #5	$209.77	10.355%	$231.4917	$231.49	$231.50	$231.50
Purchase #6	$119.98	11.355%	$133.6037	$133.60	$133.60	$133.60
Purchase #7	$6.33	11.454%	$7.055	$7.06	$7.05	$7.10
7 purchase totals =	$895.30		$996.3847	$996.39	$996.35	$996.50