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	$130.85	10.442%	$144.5134	$144.51	$144.50	$144.50
Purchase #2	$190.97	11.397%	$212.7349	$212.73	$212.75	$212.70
Purchase #3	$224.58	6.866%	$239.9997	$240.00	$240.00	$240.00
Purchase #4	$77.25	7.332%	$82.914	$82.91	$82.90	$82.90
Purchase #5	$88.44	7.609%	$95.1694	$95.17	$95.15	$95.20
Purchase #6	$161.52	4.579%	$168.916	$168.92	$168.90	$168.90
Purchase #7	$53.78	5.343%	$56.6535	$56.65	$56.65	$56.70
7 purchase totals =	$927.39		$1,000.9009	$1,000.89	$1,000.85	$1,000.90