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	$127.99	9.496%	$140.1439	$140.14	$140.15	$140.10
Purchase #2	$68.88	10.703%	$76.2522	$76.25	$76.25	$76.30
Purchase #3	$242.60	13.519%	$275.3971	$275.40	$275.40	$275.40
Purchase #4	$115.36	13.473%	$130.9025	$130.90	$130.90	$130.90
Purchase #5	$184.31	6.505%	$196.2994	$196.30	$196.30	$196.30
Purchase #6	$101.51	13.151%	$114.8596	$114.86	$114.85	$114.90
Purchase #7	$46.60	10.378%	$51.4361	$51.44	$51.45	$51.40
7 purchase totals =	$887.25		$985.2908	$985.29	$985.30	$985.30