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	$172.34	7.462%	$185.2	$185.20	$185.20	$185.20
Purchase #2	$200.72	9.516%	$219.8205	$219.82	$219.80	$219.80
Purchase #3	$99.88	3.381%	$103.2569	$103.26	$103.25	$103.30
Purchase #4	$224.35	10.421%	$247.7295	$247.73	$247.75	$247.70
Purchase #5	$88.62	4.572%	$92.6717	$92.67	$92.65	$92.70
Purchase #6	$161.32	6.779%	$172.2559	$172.26	$172.25	$172.30
Purchase #7	$57.83	9.529%	$63.3406	$63.34	$63.35	$63.30
7 purchase totals =	$1,005.06		$1,084.2751	$1,084.28	$1,084.25	$1,084.30