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	$193.85	8.715%	$210.744	$210.74	$210.75	$210.70
Purchase #2	$119.57	7.606%	$128.6645	$128.66	$128.65	$128.70
Purchase #3	$40.90	4.728%	$42.8338	$42.83	$42.85	$42.80
Purchase #4	$169.79	11.841%	$189.8948	$189.89	$189.90	$189.90
Purchase #5	$90.85	9.558%	$99.5334	$99.53	$99.55	$99.50
Purchase #6	$18.50	7.467%	$19.8814	$19.88	$19.90	$19.90
Purchase #7	$135.70	7.771%	$146.2452	$146.25	$146.25	$146.20
7 purchase totals =	$769.16		$837.7971	$837.78	$837.85	$837.70