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	$183.42	11.124%	$203.8236	$203.82	$203.80	$203.80
Purchase #2	$164.90	13.685%	$187.4666	$187.47	$187.45	$187.50
Purchase #3	$85.81	5.147%	$90.2266	$90.23	$90.25	$90.20
Purchase #4	$137.43	11.796%	$153.6412	$153.64	$153.65	$153.60
Purchase #5	$95.66	7.576%	$102.9072	$102.91	$102.90	$102.90
Purchase #6	$196.92	7.394%	$211.4803	$211.48	$211.50	$211.50
Purchase #7	$219.82	10.765%	$243.4836	$243.48	$243.50	$243.50
7 purchase totals =	$1,083.96		$1,193.0291	$1,193.03	$1,193.05	$1,193.00