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	$170.92	7.526%	$183.7834	$183.78	$183.80	$183.80
Purchase #2	$88.69	11.674%	$99.0437	$99.04	$99.05	$99.00
Purchase #3	$83.48	11.306%	$92.9182	$92.92	$92.90	$92.90
Purchase #4	$151.34	11.666%	$168.9953	$169.00	$169.00	$169.00
Purchase #5	$50.57	4.283%	$52.7359	$52.74	$52.75	$52.70
Purchase #6	$70.72	3.219%	$72.9965	$73.00	$73.00	$73.00
Purchase #7	$59.47	3.163%	$61.351	$61.35	$61.35	$61.40
7 purchase totals =	$675.19		$731.8240	$731.83	$731.85	$731.80