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	$152.58	10.650%	$168.8298	$168.83	$168.85	$168.80
Purchase #2	$147.79	12.683%	$166.5342	$166.53	$166.55	$166.50
Purchase #3	$6.39	12.342%	$7.1787	$7.18	$7.20	$7.20
Purchase #4	$113.69	4.419%	$118.714	$118.71	$118.70	$118.70
Purchase #5	$201.57	3.772%	$209.1732	$209.17	$209.15	$209.20
Purchase #6	$169.88	6.145%	$180.3191	$180.32	$180.30	$180.30
Purchase #7	$52.37	13.257%	$59.3127	$59.31	$59.30	$59.30
7 purchase totals =	$844.27		$910.0617	$910.05	$910.05	$910.00