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	$223.60	8.611%	$242.8542	$242.85	$242.85	$242.90
Purchase #2	$92.79	11.581%	$103.536	$103.54	$103.55	$103.50
Purchase #3	$102.96	13.436%	$116.7937	$116.79	$116.80	$116.80
Purchase #4	$36.62	6.150%	$38.8721	$38.87	$38.85	$38.90
Purchase #5	$220.37	10.560%	$243.6411	$243.64	$243.65	$243.60
Purchase #6	$51.98	6.241%	$55.2241	$55.22	$55.20	$55.20
Purchase #7	$187.77	11.566%	$209.4875	$209.49	$209.50	$209.50
7 purchase totals =	$916.09		$1,010.4087	$1,010.40	$1,010.40	$1,010.40