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	$135.70	4.523%	$141.8377	$141.84	$141.85	$141.80
Purchase #2	$157.87	8.817%	$171.7894	$171.79	$171.80	$171.80
Purchase #3	$250.85	12.266%	$281.6193	$281.62	$281.60	$281.60
Purchase #4	$49.58	7.480%	$53.2886	$53.29	$53.30	$53.30
Purchase #5	$233.30	13.380%	$264.5155	$264.52	$264.50	$264.50
Purchase #6	$85.55	7.174%	$91.6874	$91.69	$91.70	$91.70
Purchase #7	$143.69	5.578%	$151.705	$151.71	$151.70	$151.70
7 purchase totals =	$1,056.54		$1,156.4429	$1,156.46	$1,156.45	$1,156.40