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	$130.61	5.272%	$137.4958	$137.50	$137.50	$137.50
Purchase #2	$89.40	6.282%	$95.0161	$95.02	$95.00	$95.00
Purchase #3	$234.60	12.751%	$264.5138	$264.51	$264.50	$264.50
Purchase #4	$12.36	6.364%	$13.1466	$13.15	$13.15	$13.10
Purchase #5	$13.50	8.166%	$14.6024	$14.60	$14.60	$14.60
Purchase #6	$30.68	3.637%	$31.7958	$31.80	$31.80	$31.80
Purchase #7	$215.86	13.559%	$245.1285	$245.13	$245.15	$245.10
7 purchase totals =	$727.01		$801.6990	$801.71	$801.70	$801.60