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	$230.97	4.429%	$241.1997	$241.20	$241.20	$241.20
Purchase #2	$102.60	11.443%	$114.3405	$114.34	$114.35	$114.30
Purchase #3	$36.32	11.608%	$40.536	$40.54	$40.55	$40.50
Purchase #4	$102.34	12.164%	$114.7886	$114.79	$114.80	$114.80
Purchase #5	$152.56	12.643%	$171.8482	$171.85	$171.85	$171.80
Purchase #6	$130.66	10.645%	$144.5688	$144.57	$144.55	$144.60
Purchase #7	$102.91	11.251%	$114.4884	$114.49	$114.50	$114.50
7 purchase totals =	$858.36		$941.7702	$941.78	$941.80	$941.70