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	$101.30	12.655%	$114.1195	$114.12	$114.10	$114.10
Purchase #2	$98.33	5.130%	$103.3743	$103.37	$103.35	$103.40
Purchase #3	$220.73	9.491%	$241.6795	$241.68	$241.70	$241.70
Purchase #4	$33.86	10.658%	$37.4688	$37.47	$37.45	$37.50
Purchase #5	$38.58	11.628%	$43.0661	$43.07	$43.05	$43.10
Purchase #6	$124.51	4.636%	$130.2823	$130.28	$130.30	$130.30
Purchase #7	$90.53	11.414%	$100.8631	$100.86	$100.85	$100.90
7 purchase totals =	$707.84		$770.8536	$770.85	$770.80	$771.00