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	$192.82	13.525%	$218.8989	$218.90	$218.90	$218.90
Purchase #2	$41.69	5.236%	$43.8729	$43.87	$43.85	$43.90
Purchase #3	$35.72	9.610%	$39.1527	$39.15	$39.15	$39.20
Purchase #4	$82.99	3.447%	$85.8507	$85.85	$85.85	$85.90
Purchase #5	$74.56	11.812%	$83.367	$83.37	$83.35	$83.40
Purchase #6	$21.94	9.872%	$24.1059	$24.11	$24.10	$24.10
Purchase #7	$36.44	9.850%	$40.0293	$40.03	$40.05	$40.00
7 purchase totals =	$486.16		$535.2774	$535.28	$535.25	$535.40