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	$168.68	12.559%	$189.8645	$189.86	$189.85	$189.90
Purchase #2	$65.69	6.190%	$69.7562	$69.76	$69.75	$69.80
Purchase #3	$62.58	11.874%	$70.0107	$70.01	$70.00	$70.00
Purchase #4	$131.72	10.180%	$145.1291	$145.13	$145.15	$145.10
Purchase #5	$238.71	6.268%	$253.6723	$253.67	$253.65	$253.70
Purchase #6	$158.92	5.874%	$168.255	$168.26	$168.25	$168.30
Purchase #7	$89.40	11.439%	$99.6265	$99.63	$99.65	$99.60
7 purchase totals =	$915.70		$996.3143	$996.32	$996.30	$996.40