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	$133.63	12.506%	$150.3418	$150.34	$150.35	$150.30
Purchase #2	$111.69	4.394%	$116.5977	$116.60	$116.60	$116.60
Purchase #3	$192.47	6.547%	$205.071	$205.07	$205.05	$205.10
Purchase #4	$63.27	13.532%	$71.8317	$71.83	$71.85	$71.80
Purchase #5	$167.73	7.745%	$180.7207	$180.72	$180.70	$180.70
Purchase #6	$197.40	6.649%	$210.5251	$210.53	$210.55	$210.50
Purchase #7	$29.97	3.629%	$31.0576	$31.06	$31.05	$31.10
7 purchase totals =	$896.16		$966.1456	$966.15	$966.15	$966.10