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	$193.47	3.596%	$200.4272	$200.43	$200.45	$200.40
Purchase #2	$89.73	3.774%	$93.1164	$93.12	$93.10	$93.10
Purchase #3	$25.68	8.369%	$27.8292	$27.83	$27.85	$27.80
Purchase #4	$148.31	11.856%	$165.8936	$165.89	$165.90	$165.90
Purchase #5	$80.93	11.212%	$90.0039	$90.00	$90.00	$90.00
Purchase #6	$69.90	4.748%	$73.2189	$73.22	$73.20	$73.20
Purchase #7	$152.34	13.320%	$172.6317	$172.63	$172.65	$172.60
7 purchase totals =	$760.36		$823.1209	$823.12	$823.15	$823.00