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	$56.55	3.548%	$58.5564	$58.56	$58.55	$58.60
Purchase #2	$191.44	4.185%	$199.4518	$199.45	$199.45	$199.50
Purchase #3	$14.28	6.672%	$15.2328	$15.23	$15.25	$15.20
Purchase #4	$227.39	7.534%	$244.5216	$244.52	$244.50	$244.50
Purchase #5	$125.50	3.458%	$129.8398	$129.84	$129.85	$129.80
Purchase #6	$148.34	5.453%	$156.429	$156.43	$156.45	$156.40
Purchase #7	$88.41	13.695%	$100.5177	$100.52	$100.50	$100.50
7 purchase totals =	$851.91		$904.5491	$904.55	$904.55	$904.50