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	$68.58	5.168%	$72.1242	$72.12	$72.10	$72.10
Purchase #2	$158.89	12.282%	$178.4049	$178.40	$178.40	$178.40
Purchase #3	$212.79	7.825%	$229.4408	$229.44	$229.45	$229.40
Purchase #4	$236.41	8.480%	$256.4576	$256.46	$256.45	$256.50
Purchase #5	$204.49	8.552%	$221.978	$221.98	$222.00	$222.00
Purchase #6	$212.52	3.257%	$219.4418	$219.44	$219.45	$219.40
Purchase #7	$52.72	13.294%	$59.7286	$59.73	$59.75	$59.70
7 purchase totals =	$1,146.40		$1,237.5759	$1,237.57	$1,237.60	$1,237.50