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	$146.56	5.144%	$154.099	$154.10	$154.10	$154.10
Purchase #2	$168.42	9.312%	$184.1033	$184.10	$184.10	$184.10
Purchase #3	$138.37	12.695%	$155.9361	$155.94	$155.95	$155.90
Purchase #4	$139.72	7.855%	$150.695	$150.70	$150.70	$150.70
Purchase #5	$154.61	10.841%	$171.3713	$171.37	$171.35	$171.40
Purchase #6	$209.88	6.727%	$223.9986	$224.00	$224.00	$224.00
Purchase #7	$200.61	7.424%	$215.5033	$215.50	$215.50	$215.50
7 purchase totals =	$1,158.17		$1,255.7066	$1,255.71	$1,255.70	$1,255.70