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	$106.34	5.437%	$112.1217	$112.12	$112.10	$112.10
Purchase #2	$72.78	8.196%	$78.745	$78.75	$78.75	$78.70
Purchase #3	$64.53	7.319%	$69.253	$69.25	$69.25	$69.30
Purchase #4	$135.95	5.136%	$142.9324	$142.93	$142.95	$142.90
Purchase #5	$122.73	13.590%	$139.409	$139.41	$139.40	$139.40
Purchase #6	$45.98	9.813%	$50.492	$50.49	$50.50	$50.50
Purchase #7	$74.90	11.695%	$83.6596	$83.66	$83.65	$83.70
7 purchase totals =	$623.21		$676.6127	$676.61	$676.60	$676.60