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	$197.59	10.768%	$218.8665	$218.87	$218.85	$218.90
Purchase #2	$110.52	5.330%	$116.4107	$116.41	$116.40	$116.40
Purchase #3	$98.62	13.457%	$111.8913	$111.89	$111.90	$111.90
Purchase #4	$56.71	4.622%	$59.3311	$59.33	$59.35	$59.30
Purchase #5	$216.68	9.422%	$237.0956	$237.10	$237.10	$237.10
Purchase #6	$85.60	8.405%	$92.7947	$92.79	$92.80	$92.80
Purchase #7	$106.84	9.799%	$117.3093	$117.31	$117.30	$117.30
7 purchase totals =	$872.56		$953.6992	$953.70	$953.70	$953.70