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	$55.81	6.156%	$59.2457	$59.25	$59.25	$59.20
Purchase #2	$24.70	12.663%	$27.8278	$27.83	$27.85	$27.80
Purchase #3	$159.28	6.228%	$169.2	$169.20	$169.20	$169.20
Purchase #4	$98.83	11.132%	$109.8318	$109.83	$109.85	$109.80
Purchase #5	$136.97	13.487%	$155.4431	$155.44	$155.45	$155.40
Purchase #6	$194.45	6.264%	$206.6303	$206.63	$206.65	$206.60
Purchase #7	$147.38	13.629%	$167.4664	$167.47	$167.45	$167.50
7 purchase totals =	$817.42		$895.6451	$895.65	$895.70	$895.50