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	$234.84	3.212%	$242.3831	$242.38	$242.40	$242.40
Purchase #2	$87.69	3.406%	$90.6767	$90.68	$90.70	$90.70
Purchase #3	$180.70	13.439%	$204.9843	$204.98	$205.00	$205.00
Purchase #4	$133.81	6.243%	$142.1638	$142.16	$142.15	$142.20
Purchase #5	$241.56	3.796%	$250.7296	$250.73	$250.75	$250.70
Purchase #6	$30.81	8.590%	$33.4566	$33.46	$33.45	$33.50
Purchase #7	$187.27	11.539%	$208.8791	$208.88	$208.90	$208.90
7 purchase totals =	$1,096.68		$1,173.2732	$1,173.27	$1,173.35	$1,173.40