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	$84.49	4.824%	$88.5658	$88.57	$88.55	$88.60
Purchase #2	$133.52	13.388%	$151.3957	$151.40	$151.40	$151.40
Purchase #3	$56.41	6.226%	$59.9221	$59.92	$59.90	$59.90
Purchase #4	$6.77	4.253%	$7.0579	$7.06	$7.05	$7.10
Purchase #5	$80.77	13.795%	$91.9122	$91.91	$91.90	$91.90
Purchase #6	$173.26	8.145%	$187.372	$187.37	$187.35	$187.40
Purchase #7	$74.76	3.298%	$77.2256	$77.23	$77.25	$77.20
7 purchase totals =	$609.98		$663.4513	$663.46	$663.40	$663.50