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	$126.69	12.696%	$142.7746	$142.77	$142.75	$142.80
Purchase #2	$32.87	12.690%	$37.0412	$37.04	$37.05	$37.00
Purchase #3	$18.47	4.761%	$19.3494	$19.35	$19.35	$19.30
Purchase #4	$78.59	13.681%	$89.3419	$89.34	$89.35	$89.30
Purchase #5	$64.94	10.597%	$71.8217	$71.82	$71.80	$71.80
Purchase #6	$179.96	6.667%	$191.9579	$191.96	$191.95	$192.00
Purchase #7	$75.33	7.555%	$81.0212	$81.02	$81.00	$81.00
7 purchase totals =	$576.85		$633.3079	$633.30	$633.25	$633.20