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	$120.77	7.859%	$130.2613	$130.26	$130.25	$130.30
Purchase #2	$204.81	6.819%	$218.776	$218.78	$218.80	$218.80
Purchase #3	$73.34	11.705%	$81.9244	$81.92	$81.90	$81.90
Purchase #4	$246.65	3.745%	$255.887	$255.89	$255.90	$255.90
Purchase #5	$19.89	10.419%	$21.9623	$21.96	$21.95	$22.00
Purchase #6	$129.85	9.151%	$141.7326	$141.73	$141.75	$141.70
Purchase #7	$147.45	3.743%	$152.9691	$152.97	$152.95	$153.00
7 purchase totals =	$942.76		$1,003.5127	$1,003.51	$1,003.50	$1,003.60