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	$164.33	4.710%	$172.0699	$172.07	$172.05	$172.10
Purchase #2	$81.39	5.378%	$85.7672	$85.77	$85.75	$85.80
Purchase #3	$90.71	3.820%	$94.1751	$94.18	$94.20	$94.20
Purchase #4	$166.71	10.578%	$184.3446	$184.34	$184.35	$184.30
Purchase #5	$38.65	4.591%	$40.4244	$40.42	$40.40	$40.40
Purchase #6	$188.58	11.473%	$210.2158	$210.22	$210.20	$210.20
Purchase #7	$138.55	12.290%	$155.5778	$155.58	$155.60	$155.60
7 purchase totals =	$868.92		$942.5748	$942.58	$942.55	$942.60