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	$170.38	4.155%	$177.4593	$177.46	$177.45	$177.50
Purchase #2	$130.90	9.437%	$143.253	$143.25	$143.25	$143.30
Purchase #3	$177.27	5.681%	$187.3407	$187.34	$187.35	$187.30
Purchase #4	$69.61	4.136%	$72.4891	$72.49	$72.50	$72.50
Purchase #5	$215.38	7.737%	$232.044	$232.04	$232.05	$232.00
Purchase #6	$137.88	11.312%	$153.477	$153.48	$153.50	$153.50
Purchase #7	$125.87	10.643%	$139.2663	$139.27	$139.25	$139.30
7 purchase totals =	$1,027.29		$1,105.3294	$1,105.33	$1,105.35	$1,105.40