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	$102.92	5.766%	$108.8544	$108.85	$108.85	$108.90
Purchase #2	$186.70	6.276%	$198.4173	$198.42	$198.40	$198.40
Purchase #3	$213.51	5.113%	$224.4268	$224.43	$224.45	$224.40
Purchase #4	$101.45	3.609%	$105.1113	$105.11	$105.10	$105.10
Purchase #5	$139.93	8.539%	$151.8786	$151.88	$151.90	$151.90
Purchase #6	$189.86	10.516%	$209.8257	$209.83	$209.85	$209.80
Purchase #7	$147.66	8.633%	$160.4075	$160.41	$160.40	$160.40
7 purchase totals =	$1,082.03		$1,158.9216	$1,158.93	$1,158.95	$1,158.90