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	$240.38	10.347%	$265.2521	$265.25	$265.25	$265.30
Purchase #2	$100.65	8.862%	$109.5696	$109.57	$109.55	$109.60
Purchase #3	$222.42	9.865%	$244.3617	$244.36	$244.35	$244.40
Purchase #4	$82.76	13.631%	$94.041	$94.04	$94.05	$94.00
Purchase #5	$218.46	13.282%	$247.4759	$247.48	$247.50	$247.50
Purchase #6	$31.71	3.677%	$32.876	$32.88	$32.90	$32.90
Purchase #7	$50.77	9.449%	$55.5673	$55.57	$55.55	$55.60
7 purchase totals =	$947.15		$1,049.1436	$1,049.15	$1,049.15	$1,049.30