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	$117.70	4.748%	$123.2884	$123.29	$123.30	$123.30
Purchase #2	$220.74	9.774%	$242.3151	$242.32	$242.30	$242.30
Purchase #3	$49.78	4.256%	$51.8986	$51.90	$51.90	$51.90
Purchase #4	$121.29	13.116%	$137.1984	$137.20	$137.20	$137.20
Purchase #5	$228.92	6.252%	$243.2321	$243.23	$243.25	$243.20
Purchase #6	$171.72	13.621%	$195.11	$195.11	$195.10	$195.10
Purchase #7	$22.42	9.250%	$24.4939	$24.49	$24.50	$24.50
7 purchase totals =	$932.57		$1,017.5365	$1,017.54	$1,017.55	$1,017.50