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	$110.45	7.341%	$118.5581	$118.56	$118.55	$118.60
Purchase #2	$140.72	4.132%	$146.5346	$146.53	$146.55	$146.50
Purchase #3	$9.43	12.339%	$10.5936	$10.59	$10.60	$10.60
Purchase #4	$74.60	10.240%	$82.239	$82.24	$82.25	$82.20
Purchase #5	$236.33	3.665%	$244.9915	$244.99	$245.00	$245.00
Purchase #6	$220.36	3.578%	$228.2445	$228.24	$228.25	$228.20
Purchase #7	$97.89	13.216%	$110.8271	$110.83	$110.85	$110.80
7 purchase totals =	$889.78		$941.9884	$941.98	$942.05	$941.90