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	$221.89	9.114%	$242.1131	$242.11	$242.10	$242.10
Purchase #2	$85.82	4.336%	$89.5412	$89.54	$89.55	$89.50
Purchase #3	$53.91	10.532%	$59.5878	$59.59	$59.60	$59.60
Purchase #4	$97.96	8.218%	$106.0104	$106.01	$106.00	$106.00
Purchase #5	$93.53	10.587%	$103.432	$103.43	$103.45	$103.40
Purchase #6	$96.94	3.287%	$100.1264	$100.13	$100.15	$100.10
Purchase #7	$199.49	13.806%	$227.0316	$227.03	$227.05	$227.00
7 purchase totals =	$849.54		$927.8425	$927.84	$927.90	$927.70