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	$139.40	4.219%	$145.2813	$145.28	$145.30	$145.30
Purchase #2	$122.43	13.296%	$138.7083	$138.71	$138.70	$138.70
Purchase #3	$160.86	13.293%	$182.2431	$182.24	$182.25	$182.20
Purchase #4	$81.85	4.569%	$85.5897	$85.59	$85.60	$85.60
Purchase #5	$128.47	11.468%	$143.2029	$143.20	$143.20	$143.20
Purchase #6	$245.94	7.452%	$264.2674	$264.27	$264.25	$264.30
Purchase #7	$78.42	12.665%	$88.3519	$88.35	$88.35	$88.40
7 purchase totals =	$957.37		$1,047.6446	$1,047.64	$1,047.65	$1,047.70