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	$127.86	12.440%	$143.7658	$143.77	$143.75	$143.80
Purchase #2	$155.55	12.510%	$175.0093	$175.01	$175.00	$175.00
Purchase #3	$105.42	12.300%	$118.3867	$118.39	$118.40	$118.40
Purchase #4	$97.87	3.725%	$101.5157	$101.52	$101.50	$101.50
Purchase #5	$218.31	13.674%	$248.1617	$248.16	$248.15	$248.20
Purchase #6	$142.93	3.229%	$147.5452	$147.55	$147.55	$147.50
Purchase #7	$141.89	12.653%	$159.8433	$159.84	$159.85	$159.80
7 purchase totals =	$989.83		$1,094.2277	$1,094.24	$1,094.20	$1,094.20