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	$148.46	3.322%	$153.3918	$153.39	$153.40	$153.40
Purchase #2	$245.46	4.405%	$256.2725	$256.27	$256.25	$256.30
Purchase #3	$222.55	11.739%	$248.6751	$248.68	$248.70	$248.70
Purchase #4	$33.86	11.582%	$37.7817	$37.78	$37.80	$37.80
Purchase #5	$21.30	7.457%	$22.8883	$22.89	$22.90	$22.90
Purchase #6	$52.42	7.844%	$56.5318	$56.53	$56.55	$56.50
Purchase #7	$111.48	8.506%	$120.9625	$120.96	$120.95	$121.00
7 purchase totals =	$835.53		$896.5037	$896.50	$896.55	$896.60