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	$205.76	13.426%	$233.3853	$233.39	$233.40	$233.40
Purchase #2	$198.43	12.803%	$223.835	$223.84	$223.85	$223.80
Purchase #3	$135.92	5.298%	$143.121	$143.12	$143.10	$143.10
Purchase #4	$173.56	13.179%	$196.4335	$196.43	$196.45	$196.40
Purchase #5	$168.61	4.126%	$175.5668	$175.57	$175.55	$175.60
Purchase #6	$52.80	8.206%	$57.1328	$57.13	$57.15	$57.10
Purchase #7	$180.25	7.350%	$193.4984	$193.50	$193.50	$193.50
7 purchase totals =	$1,115.33		$1,222.9728	$1,222.98	$1,223.00	$1,222.90