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	$150.44	4.129%	$156.6517	$156.65	$156.65	$156.70
Purchase #2	$147.75	12.465%	$166.167	$166.17	$166.15	$166.20
Purchase #3	$240.40	6.611%	$256.2928	$256.29	$256.30	$256.30
Purchase #4	$182.53	5.105%	$191.8482	$191.85	$191.85	$191.80
Purchase #5	$134.69	3.305%	$139.1415	$139.14	$139.15	$139.10
Purchase #6	$126.54	4.607%	$132.3697	$132.37	$132.35	$132.40
Purchase #7	$98.34	11.142%	$109.297	$109.30	$109.30	$109.30
7 purchase totals =	$1,080.69		$1,151.7679	$1,151.77	$1,151.75	$1,151.80