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	$192.83	6.628%	$205.6108	$205.61	$205.60	$205.60
Purchase #2	$138.94	5.852%	$147.0708	$147.07	$147.05	$147.10
Purchase #3	$244.69	7.328%	$262.6209	$262.62	$262.60	$262.60
Purchase #4	$185.56	7.732%	$199.9075	$199.91	$199.90	$199.90
Purchase #5	$18.60	12.319%	$20.8913	$20.89	$20.90	$20.90
Purchase #6	$54.73	4.269%	$57.0664	$57.07	$57.05	$57.10
Purchase #7	$198.95	9.686%	$218.2203	$218.22	$218.20	$218.20
7 purchase totals =	$1,034.30		$1,111.3880	$1,111.39	$1,111.30	$1,111.40