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	$56.56	5.809%	$59.8456	$59.85	$59.85	$59.80
Purchase #2	$209.38	6.470%	$222.9269	$222.93	$222.95	$222.90
Purchase #3	$69.52	5.284%	$73.1934	$73.19	$73.20	$73.20
Purchase #4	$32.33	7.357%	$34.7085	$34.71	$34.70	$34.70
Purchase #5	$52.59	11.761%	$58.7751	$58.78	$58.80	$58.80
Purchase #6	$154.82	4.719%	$162.126	$162.13	$162.15	$162.10
Purchase #7	$218.53	9.766%	$239.8716	$239.87	$239.85	$239.90
7 purchase totals =	$793.73		$851.4471	$851.46	$851.50	$851.40