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	$236.33	12.200%	$265.1623	$265.16	$265.15	$265.20
Purchase #2	$44.97	3.489%	$46.539	$46.54	$46.55	$46.50
Purchase #3	$225.38	13.512%	$255.8333	$255.83	$255.85	$255.80
Purchase #4	$109.76	12.536%	$123.5195	$123.52	$123.50	$123.50
Purchase #5	$64.63	4.439%	$67.4989	$67.50	$67.50	$67.50
Purchase #6	$216.31	3.206%	$223.2449	$223.24	$223.25	$223.20
Purchase #7	$73.42	3.535%	$76.0154	$76.02	$76.00	$76.00
7 purchase totals =	$970.80		$1,057.8133	$1,057.81	$1,057.80	$1,057.70