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	$112.35	5.485%	$118.5124	$118.51	$118.50	$118.50
Purchase #2	$61.46	5.789%	$65.0179	$65.02	$65.00	$65.00
Purchase #3	$55.51	5.500%	$58.5631	$58.56	$58.55	$58.60
Purchase #4	$185.45	3.180%	$191.3473	$191.35	$191.35	$191.30
Purchase #5	$204.61	4.608%	$214.0384	$214.04	$214.05	$214.00
Purchase #6	$131.96	7.781%	$142.2278	$142.23	$142.25	$142.20
Purchase #7	$131.26	13.435%	$148.8948	$148.89	$148.90	$148.90
7 purchase totals =	$882.60		$938.6017	$938.60	$938.60	$938.50