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	$185.53	8.248%	$200.8325	$200.83	$200.85	$200.80
Purchase #2	$58.81	11.192%	$65.392	$65.39	$65.40	$65.40
Purchase #3	$75.26	13.495%	$85.4163	$85.42	$85.40	$85.40
Purchase #4	$241.46	7.163%	$258.7558	$258.76	$258.75	$258.80
Purchase #5	$211.80	4.111%	$220.5071	$220.51	$220.50	$220.50
Purchase #6	$214.45	13.284%	$242.9375	$242.94	$242.95	$242.90
Purchase #7	$174.31	4.772%	$182.6281	$182.63	$182.65	$182.60
7 purchase totals =	$1,161.62		$1,256.4693	$1,256.48	$1,256.50	$1,256.40