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	$38.25	6.606%	$40.7768	$40.78	$40.80	$40.80
Purchase #2	$148.86	3.642%	$154.2815	$154.28	$154.30	$154.30
Purchase #3	$55.54	6.452%	$59.1234	$59.12	$59.10	$59.10
Purchase #4	$36.90	4.501%	$38.5609	$38.56	$38.55	$38.60
Purchase #5	$120.79	7.398%	$129.726	$129.73	$129.75	$129.70
Purchase #6	$17.79	13.143%	$20.1281	$20.13	$20.15	$20.10
Purchase #7	$23.77	13.187%	$26.9045	$26.90	$26.90	$26.90
7 purchase totals =	$441.90		$469.5012	$469.50	$469.55	$469.50