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	$72.37	6.480%	$77.0596	$77.06	$77.05	$77.10
Purchase #2	$146.92	3.408%	$151.927	$151.93	$151.95	$151.90
Purchase #3	$55.79	11.406%	$62.1534	$62.15	$62.15	$62.20
Purchase #4	$59.46	11.214%	$66.1278	$66.13	$66.15	$66.10
Purchase #5	$59.84	12.869%	$67.5408	$67.54	$67.55	$67.50
Purchase #6	$224.51	6.833%	$239.8508	$239.85	$239.85	$239.90
Purchase #7	$35.59	12.610%	$40.0779	$40.08	$40.10	$40.10
7 purchase totals =	$654.48		$704.7373	$704.74	$704.80	$704.80