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	$210.64	7.334%	$226.0883	$226.09	$226.10	$226.10
Purchase #2	$61.96	13.603%	$70.3884	$70.39	$70.40	$70.40
Purchase #3	$101.89	11.498%	$113.6053	$113.61	$113.60	$113.60
Purchase #4	$81.41	13.492%	$92.3938	$92.39	$92.40	$92.40
Purchase #5	$173.31	7.271%	$185.9114	$185.91	$185.90	$185.90
Purchase #6	$224.95	9.448%	$246.2033	$246.20	$246.20	$246.20
Purchase #7	$52.46	13.846%	$59.7236	$59.72	$59.70	$59.70
7 purchase totals =	$906.62		$994.3141	$994.31	$994.30	$994.30