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	$86.47	9.589%	$94.7616	$94.76	$94.75	$94.80
Purchase #2	$196.53	13.374%	$222.8139	$222.81	$222.80	$222.80
Purchase #3	$148.55	9.676%	$162.9237	$162.92	$162.90	$162.90
Purchase #4	$230.92	11.173%	$256.7207	$256.72	$256.70	$256.70
Purchase #5	$87.90	10.288%	$96.9432	$96.94	$96.95	$96.90
Purchase #6	$142.90	4.431%	$149.2319	$149.23	$149.25	$149.20
Purchase #7	$88.92	11.729%	$99.3494	$99.35	$99.35	$99.30
7 purchase totals =	$982.19		$1,082.7444	$1,082.73	$1,082.70	$1,082.60