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	$216.70	10.128%	$238.6474	$238.65	$238.65	$238.60
Purchase #2	$98.63	11.789%	$110.2575	$110.26	$110.25	$110.30
Purchase #3	$224.26	13.872%	$255.3693	$255.37	$255.35	$255.40
Purchase #4	$103.98	9.322%	$113.673	$113.67	$113.65	$113.70
Purchase #5	$9.96	7.162%	$10.6733	$10.67	$10.65	$10.70
Purchase #6	$54.86	7.814%	$59.1468	$59.15	$59.15	$59.10
Purchase #7	$75.26	9.607%	$82.4902	$82.49	$82.50	$82.50
7 purchase totals =	$783.65		$870.2575	$870.26	$870.20	$870.30