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	$224.73	7.247%	$241.0162	$241.02	$241.00	$241.00
Purchase #2	$55.92	10.539%	$61.8134	$61.81	$61.80	$61.80
Purchase #3	$53.43	12.170%	$59.9324	$59.93	$59.95	$59.90
Purchase #4	$222.54	6.218%	$236.3775	$236.38	$236.40	$236.40
Purchase #5	$29.93	6.785%	$31.9608	$31.96	$31.95	$32.00
Purchase #6	$67.50	5.392%	$71.1396	$71.14	$71.15	$71.10
Purchase #7	$32.29	11.342%	$35.9523	$35.95	$35.95	$36.00
7 purchase totals =	$686.34		$738.1922	$738.19	$738.20	$738.20