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	$77.89	7.415%	$83.6655	$83.67	$83.65	$83.70
Purchase #2	$59.99	3.637%	$62.1718	$62.17	$62.15	$62.20
Purchase #3	$195.95	13.686%	$222.7677	$222.77	$222.75	$222.80
Purchase #4	$46.50	10.373%	$51.3234	$51.32	$51.30	$51.30
Purchase #5	$99.61	7.161%	$106.7431	$106.74	$106.75	$106.70
Purchase #6	$209.84	10.478%	$231.827	$231.83	$231.85	$231.80
Purchase #7	$161.49	10.466%	$178.3915	$178.39	$178.40	$178.40
7 purchase totals =	$851.27		$936.8900	$936.89	$936.85	$936.90