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	$210.58	5.799%	$222.7915	$222.79	$222.80	$222.80
Purchase #2	$148.81	4.568%	$155.6076	$155.61	$155.60	$155.60
Purchase #3	$218.71	10.655%	$242.0136	$242.01	$242.00	$242.00
Purchase #4	$108.41	7.360%	$116.389	$116.39	$116.40	$116.40
Purchase #5	$148.89	11.553%	$166.0913	$166.09	$166.10	$166.10
Purchase #6	$104.76	7.427%	$112.5405	$112.54	$112.55	$112.50
Purchase #7	$68.65	3.579%	$71.107	$71.11	$71.10	$71.10
7 purchase totals =	$1,008.81		$1,086.5405	$1,086.54	$1,086.55	$1,086.50