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	$179.92	4.660%	$188.3043	$188.30	$188.30	$188.30
Purchase #2	$174.58	13.462%	$198.082	$198.08	$198.10	$198.10
Purchase #3	$125.50	13.302%	$142.194	$142.19	$142.20	$142.20
Purchase #4	$88.84	3.486%	$91.937	$91.94	$91.95	$91.90
Purchase #5	$160.51	4.510%	$167.749	$167.75	$167.75	$167.70
Purchase #6	$225.42	6.389%	$239.8221	$239.82	$239.80	$239.80
Purchase #7	$29.96	11.189%	$33.3122	$33.31	$33.30	$33.30
7 purchase totals =	$984.73		$1,061.4006	$1,061.39	$1,061.40	$1,061.30