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	$217.50	8.694%	$236.4095	$236.41	$236.40	$236.40
Purchase #2	$38.74	9.598%	$42.4583	$42.46	$42.45	$42.50
Purchase #3	$73.92	11.115%	$82.1362	$82.14	$82.15	$82.10
Purchase #4	$168.83	9.332%	$184.5852	$184.59	$184.60	$184.60
Purchase #5	$217.51	7.133%	$233.025	$233.03	$233.05	$233.00
Purchase #6	$227.59	5.277%	$239.5999	$239.60	$239.60	$239.60
Purchase #7	$23.86	6.830%	$25.4896	$25.49	$25.50	$25.50
7 purchase totals =	$967.95		$1,043.7037	$1,043.72	$1,043.75	$1,043.70