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	$69.60	13.694%	$79.131	$79.13	$79.15	$79.10
Purchase #2	$198.42	4.148%	$206.6505	$206.65	$206.65	$206.70
Purchase #3	$110.66	3.791%	$114.8551	$114.86	$114.85	$114.90
Purchase #4	$217.64	9.715%	$238.7837	$238.78	$238.80	$238.80
Purchase #5	$98.56	13.218%	$111.5877	$111.59	$111.60	$111.60
Purchase #6	$7.67	10.388%	$8.4668	$8.47	$8.45	$8.50
Purchase #7	$229.88	7.874%	$247.9808	$247.98	$248.00	$248.00
7 purchase totals =	$932.43		$1,007.4556	$1,007.46	$1,007.50	$1,007.60