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	$230.78	7.431%	$247.9293	$247.93	$247.95	$247.90
Purchase #2	$192.61	10.597%	$213.0209	$213.02	$213.00	$213.00
Purchase #3	$152.52	6.696%	$162.7327	$162.73	$162.75	$162.70
Purchase #4	$56.62	4.275%	$59.0405	$59.04	$59.05	$59.00
Purchase #5	$85.63	8.464%	$92.8777	$92.88	$92.90	$92.90
Purchase #6	$143.63	6.249%	$152.6054	$152.61	$152.60	$152.60
Purchase #7	$248.82	6.399%	$264.742	$264.74	$264.75	$264.70
7 purchase totals =	$1,110.61		$1,192.9485	$1,192.95	$1,193.00	$1,192.80