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	$49.56	6.711%	$52.886	$52.89	$52.90	$52.90
Purchase #2	$230.52	4.161%	$240.1119	$240.11	$240.10	$240.10
Purchase #3	$143.60	12.335%	$161.3131	$161.31	$161.30	$161.30
Purchase #4	$162.43	11.808%	$181.6097	$181.61	$181.60	$181.60
Purchase #5	$224.52	5.550%	$236.9809	$236.98	$237.00	$237.00
Purchase #6	$73.84	12.585%	$83.1328	$83.13	$83.15	$83.10
Purchase #7	$244.50	13.501%	$277.5099	$277.51	$277.50	$277.50
7 purchase totals =	$1,128.97		$1,233.5443	$1,233.54	$1,233.55	$1,233.50