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	$234.25	12.328%	$263.1283	$263.13	$263.15	$263.10
Purchase #2	$72.62	8.292%	$78.6417	$78.64	$78.65	$78.60
Purchase #3	$76.47	7.552%	$82.245	$82.25	$82.25	$82.20
Purchase #4	$78.65	8.415%	$85.2684	$85.27	$85.25	$85.30
Purchase #5	$22.66	9.582%	$24.8313	$24.83	$24.85	$24.80
Purchase #6	$44.28	4.829%	$46.4183	$46.42	$46.40	$46.40
Purchase #7	$199.29	7.624%	$214.4839	$214.48	$214.50	$214.50
7 purchase totals =	$728.22		$795.0169	$795.02	$795.05	$794.90