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	$168.56	11.690%	$188.2647	$188.26	$188.25	$188.30
Purchase #2	$71.32	4.251%	$74.3518	$74.35	$74.35	$74.40
Purchase #3	$220.72	4.783%	$231.277	$231.28	$231.30	$231.30
Purchase #4	$133.72	12.382%	$150.2772	$150.28	$150.30	$150.30
Purchase #5	$231.50	4.311%	$241.48	$241.48	$241.50	$241.50
Purchase #6	$131.37	7.648%	$141.4172	$141.42	$141.40	$141.40
Purchase #7	$99.74	13.259%	$112.9645	$112.96	$112.95	$113.00
7 purchase totals =	$1,056.93		$1,140.0324	$1,140.03	$1,140.05	$1,140.20