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	$243.83	9.861%	$267.8741	$267.87	$267.85	$267.90
Purchase #2	$5.64	10.556%	$6.2354	$6.24	$6.25	$6.20
Purchase #3	$148.34	7.812%	$159.9283	$159.93	$159.95	$159.90
Purchase #4	$119.54	5.300%	$125.8756	$125.88	$125.90	$125.90
Purchase #5	$78.81	6.344%	$83.8097	$83.81	$83.80	$83.80
Purchase #6	$52.68	12.468%	$59.2481	$59.25	$59.25	$59.20
Purchase #7	$61.44	9.296%	$67.1515	$67.15	$67.15	$67.20
7 purchase totals =	$710.28		$770.1227	$770.13	$770.15	$770.10