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	$48.88	7.331%	$52.4634	$52.46	$52.45	$52.50
Purchase #2	$158.59	8.791%	$172.5316	$172.53	$172.55	$172.50
Purchase #3	$115.58	9.794%	$126.8999	$126.90	$126.90	$126.90
Purchase #4	$170.95	7.221%	$183.2943	$183.29	$183.30	$183.30
Purchase #5	$90.89	11.297%	$101.1578	$101.16	$101.15	$101.20
Purchase #6	$38.28	9.581%	$41.9476	$41.95	$41.95	$41.90
Purchase #7	$110.37	11.701%	$123.2844	$123.28	$123.30	$123.30
7 purchase totals =	$733.54		$801.5790	$801.57	$801.60	$801.60