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	$97.72	8.173%	$105.7067	$105.71	$105.70	$105.70
Purchase #2	$152.85	7.490%	$164.2985	$164.30	$164.30	$164.30
Purchase #3	$153.59	11.537%	$171.3097	$171.31	$171.30	$171.30
Purchase #4	$134.57	3.302%	$139.0135	$139.01	$139.00	$139.00
Purchase #5	$245.57	7.637%	$264.3242	$264.32	$264.30	$264.30
Purchase #6	$43.52	12.507%	$48.963	$48.96	$48.95	$49.00
Purchase #7	$59.46	3.700%	$61.66	$61.66	$61.65	$61.70
7 purchase totals =	$887.28		$955.2756	$955.27	$955.20	$955.30