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	$175.94	4.651%	$184.123	$184.12	$184.10	$184.10
Purchase #2	$30.55	7.219%	$32.7554	$32.76	$32.75	$32.80
Purchase #3	$78.61	4.528%	$82.1695	$82.17	$82.15	$82.20
Purchase #4	$99.92	9.704%	$109.6162	$109.62	$109.60	$109.60
Purchase #5	$175.26	8.846%	$190.7635	$190.76	$190.75	$190.80
Purchase #6	$59.48	9.568%	$65.171	$65.17	$65.15	$65.20
Purchase #7	$118.67	13.306%	$134.4602	$134.46	$134.45	$134.50
7 purchase totals =	$738.43		$799.0588	$799.06	$798.95	$799.20