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	$175.68	13.735%	$199.8096	$199.81	$199.80	$199.80
Purchase #2	$133.86	10.480%	$147.8885	$147.89	$147.90	$147.90
Purchase #3	$203.66	4.188%	$212.1893	$212.19	$212.20	$212.20
Purchase #4	$52.88	13.267%	$59.8956	$59.90	$59.90	$59.90
Purchase #5	$131.74	12.862%	$148.6844	$148.68	$148.70	$148.70
Purchase #6	$90.50	4.288%	$94.3806	$94.38	$94.40	$94.40
Purchase #7	$199.79	6.393%	$212.5626	$212.56	$212.55	$212.60
7 purchase totals =	$988.11		$1,075.4106	$1,075.41	$1,075.45	$1,075.50