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	$146.92	8.427%	$159.3009	$159.30	$159.30	$159.30
Purchase #2	$103.49	13.562%	$117.5253	$117.53	$117.55	$117.50
Purchase #3	$39.34	10.491%	$43.4672	$43.47	$43.45	$43.50
Purchase #4	$102.88	6.262%	$109.3223	$109.32	$109.30	$109.30
Purchase #5	$176.33	9.208%	$192.5665	$192.57	$192.55	$192.60
Purchase #6	$232.59	5.631%	$245.6871	$245.69	$245.70	$245.70
Purchase #7	$171.87	4.156%	$179.0129	$179.01	$179.00	$179.00
7 purchase totals =	$973.42		$1,046.8822	$1,046.89	$1,046.85	$1,046.90