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	$117.39	6.429%	$124.937	$124.94	$124.95	$124.90
Purchase #2	$79.80	11.821%	$89.2332	$89.23	$89.25	$89.20
Purchase #3	$89.43	12.104%	$100.2546	$100.25	$100.25	$100.30
Purchase #4	$86.72	3.561%	$89.8081	$89.81	$89.80	$89.80
Purchase #5	$211.32	6.549%	$225.1593	$225.16	$225.15	$225.20
Purchase #6	$210.76	12.725%	$237.5792	$237.58	$237.60	$237.60
Purchase #7	$16.63	4.815%	$17.4307	$17.43	$17.45	$17.40
7 purchase totals =	$812.05		$884.4021	$884.40	$884.45	$884.40