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	$65.70	10.406%	$72.5367	$72.54	$72.55	$72.50
Purchase #2	$144.51	5.269%	$152.1242	$152.12	$152.10	$152.10
Purchase #3	$172.25	9.290%	$188.252	$188.25	$188.25	$188.30
Purchase #4	$93.41	8.456%	$101.3087	$101.31	$101.30	$101.30
Purchase #5	$103.63	10.493%	$114.5039	$114.50	$114.50	$114.50
Purchase #6	$180.61	8.158%	$195.3442	$195.34	$195.35	$195.30
Purchase #7	$163.32	13.317%	$185.0693	$185.07	$185.05	$185.10
7 purchase totals =	$923.43		$1,009.1390	$1,009.13	$1,009.10	$1,009.10