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	$54.44	9.775%	$59.7615	$59.76	$59.75	$59.80
Purchase #2	$83.62	5.547%	$88.2584	$88.26	$88.25	$88.30
Purchase #3	$71.56	9.747%	$78.535	$78.54	$78.55	$78.50
Purchase #4	$15.58	3.363%	$16.104	$16.10	$16.10	$16.10
Purchase #5	$131.31	8.158%	$142.0223	$142.02	$142.00	$142.00
Purchase #6	$69.67	11.589%	$77.7441	$77.74	$77.75	$77.70
Purchase #7	$119.32	6.725%	$127.3443	$127.34	$127.35	$127.30
7 purchase totals =	$545.50		$589.7696	$589.76	$589.75	$589.70