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	$100.68	8.421%	$109.1583	$109.16	$109.15	$109.20
Purchase #2	$33.45	11.166%	$37.185	$37.19	$37.20	$37.20
Purchase #3	$152.88	13.179%	$173.0281	$173.03	$173.05	$173.00
Purchase #4	$89.64	4.853%	$93.9902	$93.99	$94.00	$94.00
Purchase #5	$196.79	7.170%	$210.8998	$210.90	$210.90	$210.90
Purchase #6	$57.67	7.681%	$62.0996	$62.10	$62.10	$62.10
Purchase #7	$76.65	7.434%	$82.3482	$82.35	$82.35	$82.30
7 purchase totals =	$707.76		$768.7092	$768.72	$768.75	$768.70