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	$177.79	11.503%	$198.2412	$198.24	$198.25	$198.20
Purchase #2	$65.94	10.383%	$72.7866	$72.79	$72.80	$72.80
Purchase #3	$18.47	4.808%	$19.358	$19.36	$19.35	$19.40
Purchase #4	$246.49	10.727%	$272.931	$272.93	$272.95	$272.90
Purchase #5	$149.89	10.544%	$165.6944	$165.69	$165.70	$165.70
Purchase #6	$119.90	7.474%	$128.8613	$128.86	$128.85	$128.90
Purchase #7	$6.56	13.574%	$7.4505	$7.45	$7.45	$7.50
7 purchase totals =	$785.04		$865.3230	$865.32	$865.35	$865.40