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	$100.32	9.303%	$109.6528	$109.65	$109.65	$109.70
Purchase #2	$203.58	12.545%	$229.1191	$229.12	$229.10	$229.10
Purchase #3	$175.98	5.448%	$185.5674	$185.57	$185.55	$185.60
Purchase #4	$78.83	4.737%	$82.5642	$82.56	$82.55	$82.60
Purchase #5	$106.56	6.495%	$113.4811	$113.48	$113.50	$113.50
Purchase #6	$56.48	11.138%	$62.7707	$62.77	$62.75	$62.80
Purchase #7	$9.94	3.676%	$10.3054	$10.31	$10.30	$10.30
7 purchase totals =	$731.69		$793.4607	$793.46	$793.40	$793.60