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	$124.60	4.546%	$130.2643	$130.26	$130.25	$130.30
Purchase #2	$221.92	10.165%	$244.4782	$244.48	$244.50	$244.50
Purchase #3	$173.64	5.325%	$182.8863	$182.89	$182.90	$182.90
Purchase #4	$193.33	3.160%	$199.4392	$199.44	$199.45	$199.40
Purchase #5	$236.80	7.452%	$254.4463	$254.45	$254.45	$254.40
Purchase #6	$28.83	5.363%	$30.3762	$30.38	$30.40	$30.40
Purchase #7	$18.71	4.716%	$19.5924	$19.59	$19.60	$19.60
7 purchase totals =	$997.83		$1,061.4829	$1,061.49	$1,061.55	$1,061.50