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	$134.91	9.626%	$147.8964	$147.90	$147.90	$147.90
Purchase #2	$131.75	7.840%	$142.0792	$142.08	$142.10	$142.10
Purchase #3	$137.29	13.736%	$156.1482	$156.15	$156.15	$156.10
Purchase #4	$108.82	7.165%	$116.617	$116.62	$116.60	$116.60
Purchase #5	$219.47	10.686%	$242.9226	$242.92	$242.90	$242.90
Purchase #6	$54.98	7.238%	$58.9595	$58.96	$58.95	$59.00
Purchase #7	$109.51	6.380%	$116.4967	$116.50	$116.50	$116.50
7 purchase totals =	$896.73		$981.1196	$981.13	$981.10	$981.10