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	$155.28	4.852%	$162.8142	$162.81	$162.80	$162.80
Purchase #2	$147.77	11.436%	$164.669	$164.67	$164.65	$164.70
Purchase #3	$37.86	3.198%	$39.0708	$39.07	$39.05	$39.10
Purchase #4	$11.69	7.145%	$12.5253	$12.53	$12.55	$12.50
Purchase #5	$240.42	12.254%	$269.8811	$269.88	$269.90	$269.90
Purchase #6	$38.73	9.362%	$42.3559	$42.36	$42.35	$42.40
Purchase #7	$166.59	4.401%	$173.9216	$173.92	$173.90	$173.90
7 purchase totals =	$798.34		$865.2379	$865.24	$865.20	$865.30