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	$187.81	8.316%	$203.4283	$203.43	$203.45	$203.40
Purchase #2	$27.76	5.144%	$29.188	$29.19	$29.20	$29.20
Purchase #3	$130.31	3.503%	$134.8748	$134.87	$134.85	$134.90
Purchase #4	$174.88	13.253%	$198.0568	$198.06	$198.05	$198.10
Purchase #5	$32.91	12.598%	$37.056	$37.06	$37.05	$37.10
Purchase #6	$103.49	7.577%	$111.3314	$111.33	$111.35	$111.30
Purchase #7	$75.66	12.546%	$85.1523	$85.15	$85.15	$85.20
7 purchase totals =	$732.82		$799.0876	$799.09	$799.10	$799.20