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	$69.95	6.516%	$74.5079	$74.51	$74.50	$74.50
Purchase #2	$116.92	9.258%	$127.7445	$127.74	$127.75	$127.70
Purchase #3	$84.76	4.498%	$88.5725	$88.57	$88.55	$88.60
Purchase #4	$40.97	4.481%	$42.8059	$42.81	$42.80	$42.80
Purchase #5	$220.42	11.385%	$245.5148	$245.51	$245.50	$245.50
Purchase #6	$74.91	13.767%	$85.2229	$85.22	$85.20	$85.20
Purchase #7	$172.26	6.196%	$182.9332	$182.93	$182.95	$182.90
7 purchase totals =	$780.19		$847.3017	$847.29	$847.25	$847.20