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	$101.34	10.237%	$111.7142	$111.71	$111.70	$111.70
Purchase #2	$26.73	4.719%	$27.9914	$27.99	$28.00	$28.00
Purchase #3	$25.56	7.283%	$27.4215	$27.42	$27.40	$27.40
Purchase #4	$87.93	13.110%	$99.4576	$99.46	$99.45	$99.50
Purchase #5	$234.38	4.579%	$245.1123	$245.11	$245.10	$245.10
Purchase #6	$78.85	4.729%	$82.5788	$82.58	$82.60	$82.60
Purchase #7	$194.54	5.345%	$204.9382	$204.94	$204.95	$204.90
7 purchase totals =	$749.33		$799.2140	$799.21	$799.20	$799.20