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	$156.43	4.106%	$162.853	$162.85	$162.85	$162.90
Purchase #2	$170.71	6.568%	$181.9222	$181.92	$181.90	$181.90
Purchase #3	$119.25	3.706%	$123.6694	$123.67	$123.65	$123.70
Purchase #4	$186.83	6.769%	$199.4765	$199.48	$199.50	$199.50
Purchase #5	$42.57	7.686%	$45.8419	$45.84	$45.85	$45.80
Purchase #6	$44.25	6.551%	$47.1488	$47.15	$47.15	$47.10
Purchase #7	$144.79	8.701%	$157.3882	$157.39	$157.40	$157.40
7 purchase totals =	$864.83		$918.3000	$918.30	$918.30	$918.30