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	$210.62	13.247%	$238.5208	$238.52	$238.50	$238.50
Purchase #2	$79.93	5.163%	$84.0568	$84.06	$84.05	$84.10
Purchase #3	$9.30	11.217%	$10.3432	$10.34	$10.35	$10.30
Purchase #4	$217.36	12.152%	$243.7736	$243.77	$243.75	$243.80
Purchase #5	$158.84	6.109%	$168.5435	$168.54	$168.55	$168.50
Purchase #6	$54.72	8.166%	$59.1884	$59.19	$59.20	$59.20
Purchase #7	$144.89	9.630%	$158.8429	$158.84	$158.85	$158.80
7 purchase totals =	$875.66		$963.2692	$963.26	$963.25	$963.20