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	$142.45	7.364%	$152.94	$152.94	$152.95	$152.90
Purchase #2	$15.62	8.307%	$16.9176	$16.92	$16.90	$16.90
Purchase #3	$223.36	12.160%	$250.5206	$250.52	$250.50	$250.50
Purchase #4	$148.96	7.302%	$159.8371	$159.84	$159.85	$159.80
Purchase #5	$159.92	7.669%	$172.1843	$172.18	$172.20	$172.20
Purchase #6	$106.47	11.322%	$118.5245	$118.52	$118.50	$118.50
Purchase #7	$101.80	7.449%	$109.3831	$109.38	$109.40	$109.40
7 purchase totals =	$898.58		$980.3072	$980.30	$980.30	$980.20