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	$198.57	12.215%	$222.8253	$222.83	$222.85	$222.80
Purchase #2	$13.81	5.842%	$14.6168	$14.62	$14.60	$14.60
Purchase #3	$35.72	9.140%	$38.9848	$38.98	$39.00	$39.00
Purchase #4	$189.31	11.600%	$211.27	$211.27	$211.25	$211.30
Purchase #5	$176.41	5.657%	$186.3895	$186.39	$186.40	$186.40
Purchase #6	$29.58	12.716%	$33.3414	$33.34	$33.35	$33.30
Purchase #7	$41.35	11.341%	$46.0395	$46.04	$46.05	$46.00
7 purchase totals =	$684.75		$753.4673	$753.47	$753.50	$753.40