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	$160.66	11.249%	$178.7326	$178.73	$178.75	$178.70
Purchase #2	$184.69	5.293%	$194.4656	$194.47	$194.45	$194.50
Purchase #3	$98.31	7.170%	$105.3588	$105.36	$105.35	$105.40
Purchase #4	$105.61	13.776%	$120.1588	$120.16	$120.15	$120.20
Purchase #5	$185.47	4.390%	$193.6121	$193.61	$193.60	$193.60
Purchase #6	$163.45	9.824%	$179.5073	$179.51	$179.50	$179.50
Purchase #7	$75.40	13.814%	$85.8158	$85.82	$85.80	$85.80
7 purchase totals =	$973.59		$1,057.6510	$1,057.66	$1,057.60	$1,057.70