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	$29.26	11.325%	$32.5737	$32.57	$32.55	$32.60
Purchase #2	$95.43	4.214%	$99.4514	$99.45	$99.45	$99.50
Purchase #3	$141.94	8.728%	$154.3285	$154.33	$154.35	$154.30
Purchase #4	$119.79	6.746%	$127.871	$127.87	$127.85	$127.90
Purchase #5	$92.85	13.582%	$105.4609	$105.46	$105.45	$105.50
Purchase #6	$129.71	8.853%	$141.1932	$141.19	$141.20	$141.20
Purchase #7	$125.33	7.363%	$134.558	$134.56	$134.55	$134.60
7 purchase totals =	$734.31		$795.4367	$795.43	$795.40	$795.60