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	$81.30	13.329%	$92.1365	$92.14	$92.15	$92.10
Purchase #2	$86.42	8.874%	$94.0889	$94.09	$94.10	$94.10
Purchase #3	$155.35	10.155%	$171.1258	$171.13	$171.15	$171.10
Purchase #4	$134.93	12.731%	$152.1079	$152.11	$152.10	$152.10
Purchase #5	$40.41	12.290%	$45.3764	$45.38	$45.40	$45.40
Purchase #6	$99.71	5.826%	$105.5191	$105.52	$105.50	$105.50
Purchase #7	$105.99	12.776%	$119.5313	$119.53	$119.55	$119.50
7 purchase totals =	$704.11		$779.8859	$779.90	$779.95	$779.80