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	$103.89	6.759%	$110.9119	$110.91	$110.90	$110.90
Purchase #2	$28.74	3.676%	$29.7965	$29.80	$29.80	$29.80
Purchase #3	$196.69	11.220%	$218.7586	$218.76	$218.75	$218.80
Purchase #4	$90.95	9.628%	$99.7067	$99.71	$99.70	$99.70
Purchase #5	$148.99	13.223%	$168.6909	$168.69	$168.70	$168.70
Purchase #6	$138.91	9.303%	$151.8328	$151.83	$151.85	$151.80
Purchase #7	$227.52	13.478%	$258.1851	$258.19	$258.20	$258.20
7 purchase totals =	$935.69		$1,037.8825	$1,037.89	$1,037.90	$1,037.90