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	$56.53	8.334%	$61.2412	$61.24	$61.25	$61.20
Purchase #2	$245.38	7.501%	$263.786	$263.79	$263.80	$263.80
Purchase #3	$232.68	3.119%	$239.9373	$239.94	$239.95	$239.90
Purchase #4	$35.52	4.678%	$37.1816	$37.18	$37.20	$37.20
Purchase #5	$59.76	4.514%	$62.4576	$62.46	$62.45	$62.50
Purchase #6	$33.56	10.664%	$37.1388	$37.14	$37.15	$37.10
Purchase #7	$106.55	13.363%	$120.7883	$120.79	$120.80	$120.80
7 purchase totals =	$769.98		$822.5308	$822.54	$822.60	$822.50