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	$99.27	10.472%	$109.6656	$109.67	$109.65	$109.70
Purchase #2	$223.30	9.526%	$244.5716	$244.57	$244.55	$244.60
Purchase #3	$83.31	7.853%	$89.8523	$89.85	$89.85	$89.90
Purchase #4	$221.99	9.325%	$242.6906	$242.69	$242.70	$242.70
Purchase #5	$120.55	13.139%	$136.3891	$136.39	$136.40	$136.40
Purchase #6	$213.50	4.402%	$222.8983	$222.90	$222.90	$222.90
Purchase #7	$113.56	7.775%	$122.3893	$122.39	$122.40	$122.40
7 purchase totals =	$1,075.48		$1,168.4568	$1,168.46	$1,168.45	$1,168.60