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	$102.88	10.119%	$113.2904	$113.29	$113.30	$113.30
Purchase #2	$56.34	9.234%	$61.5424	$61.54	$61.55	$61.50
Purchase #3	$76.91	13.802%	$87.5251	$87.53	$87.55	$87.50
Purchase #4	$52.51	13.765%	$59.738	$59.74	$59.75	$59.70
Purchase #5	$232.56	7.752%	$250.5881	$250.59	$250.60	$250.60
Purchase #6	$211.71	4.684%	$221.6265	$221.63	$221.65	$221.60
Purchase #7	$77.67	7.227%	$83.2832	$83.28	$83.30	$83.30
7 purchase totals =	$810.58		$877.5937	$877.60	$877.70	$877.50