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	$146.70	6.122%	$155.681	$155.68	$155.70	$155.70
Purchase #2	$48.54	4.842%	$50.8903	$50.89	$50.90	$50.90
Purchase #3	$209.50	4.826%	$219.6105	$219.61	$219.60	$219.60
Purchase #4	$201.25	4.472%	$210.2499	$210.25	$210.25	$210.20
Purchase #5	$90.62	9.673%	$99.3857	$99.39	$99.40	$99.40
Purchase #6	$229.33	3.851%	$238.1615	$238.16	$238.15	$238.20
Purchase #7	$100.57	11.838%	$112.4755	$112.48	$112.50	$112.50
7 purchase totals =	$1,026.51		$1,086.4544	$1,086.46	$1,086.50	$1,086.50