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	$111.75	10.538%	$123.5262	$123.53	$123.55	$123.50
Purchase #2	$179.29	5.241%	$188.6866	$188.69	$188.70	$188.70
Purchase #3	$210.25	6.532%	$223.9835	$223.98	$224.00	$224.00
Purchase #4	$17.97	4.243%	$18.7325	$18.73	$18.75	$18.70
Purchase #5	$76.97	12.658%	$86.7129	$86.71	$86.70	$86.70
Purchase #6	$28.94	5.291%	$30.4712	$30.47	$30.45	$30.50
Purchase #7	$30.53	9.140%	$33.3204	$33.32	$33.30	$33.30
7 purchase totals =	$655.70		$705.4333	$705.43	$705.45	$705.40