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	$232.33	12.734%	$261.9149	$261.91	$261.90	$261.90
Purchase #2	$30.67	6.251%	$32.5872	$32.59	$32.60	$32.60
Purchase #3	$236.29	4.644%	$247.2633	$247.26	$247.25	$247.30
Purchase #4	$238.34	5.687%	$251.8944	$251.89	$251.90	$251.90
Purchase #5	$33.41	11.289%	$37.1817	$37.18	$37.20	$37.20
Purchase #6	$175.88	8.859%	$191.4612	$191.46	$191.45	$191.50
Purchase #7	$92.99	6.517%	$99.0502	$99.05	$99.05	$99.10
7 purchase totals =	$1,039.91		$1,121.3529	$1,121.34	$1,121.35	$1,121.50