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	$149.93	10.372%	$165.4807	$165.48	$165.50	$165.50
Purchase #2	$83.47	13.215%	$94.5006	$94.50	$94.50	$94.50
Purchase #3	$38.90	10.163%	$42.8534	$42.85	$42.85	$42.90
Purchase #4	$212.76	3.540%	$220.2917	$220.29	$220.30	$220.30
Purchase #5	$160.53	8.559%	$174.2698	$174.27	$174.25	$174.30
Purchase #6	$66.64	6.413%	$70.9136	$70.91	$70.90	$70.90
Purchase #7	$43.48	9.261%	$47.5067	$47.51	$47.50	$47.50
7 purchase totals =	$755.71		$815.8165	$815.81	$815.80	$815.90