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	$59.56	3.307%	$61.5296	$61.53	$61.55	$61.50
Purchase #2	$161.25	6.494%	$171.7216	$171.72	$171.70	$171.70
Purchase #3	$27.92	10.209%	$30.7704	$30.77	$30.75	$30.80
Purchase #4	$121.72	8.352%	$131.8861	$131.89	$131.90	$131.90
Purchase #5	$183.85	8.613%	$199.685	$199.69	$199.70	$199.70
Purchase #6	$21.89	13.449%	$24.834	$24.83	$24.85	$24.80
Purchase #7	$169.99	10.659%	$188.1092	$188.11	$188.10	$188.10
7 purchase totals =	$746.18		$808.5359	$808.54	$808.55	$808.50