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	$170.27	3.683%	$176.541	$176.54	$176.55	$176.50
Purchase #2	$212.29	3.213%	$219.1109	$219.11	$219.10	$219.10
Purchase #3	$62.51	13.641%	$71.037	$71.04	$71.05	$71.00
Purchase #4	$137.35	10.608%	$151.9201	$151.92	$151.90	$151.90
Purchase #5	$58.91	11.698%	$65.8013	$65.80	$65.80	$65.80
Purchase #6	$95.74	3.338%	$98.9358	$98.94	$98.95	$98.90
Purchase #7	$239.76	13.399%	$271.8854	$271.89	$271.90	$271.90
7 purchase totals =	$976.83		$1,055.2315	$1,055.24	$1,055.25	$1,055.10