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	$231.92	9.372%	$253.6555	$253.66	$253.65	$253.70
Purchase #2	$20.92	6.850%	$22.353	$22.35	$22.35	$22.40
Purchase #3	$209.92	4.329%	$219.0074	$219.01	$219.00	$219.00
Purchase #4	$53.66	10.678%	$59.3898	$59.39	$59.40	$59.40
Purchase #5	$55.85	7.263%	$59.9064	$59.91	$59.90	$59.90
Purchase #6	$74.29	8.848%	$80.8632	$80.86	$80.85	$80.90
Purchase #7	$92.90	5.321%	$97.8432	$97.84	$97.85	$97.80
7 purchase totals =	$739.46		$793.0185	$793.02	$793.00	$793.10