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	$198.88	8.255%	$215.2975	$215.30	$215.30	$215.30
Purchase #2	$18.90	13.233%	$21.401	$21.40	$21.40	$21.40
Purchase #3	$31.27	4.593%	$32.7062	$32.71	$32.70	$32.70
Purchase #4	$163.43	12.415%	$183.7198	$183.72	$183.70	$183.70
Purchase #5	$148.69	13.616%	$168.9356	$168.94	$168.95	$168.90
Purchase #6	$100.74	13.818%	$114.6603	$114.66	$114.65	$114.70
Purchase #7	$73.29	13.450%	$83.1475	$83.15	$83.15	$83.10
7 purchase totals =	$735.20		$819.8679	$819.88	$819.85	$819.80