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	$65.75	3.213%	$67.8625	$67.86	$67.85	$67.90
Purchase #2	$42.68	6.787%	$45.5767	$45.58	$45.60	$45.60
Purchase #3	$7.34	13.251%	$8.3126	$8.31	$8.30	$8.30
Purchase #4	$98.48	3.467%	$101.8943	$101.89	$101.90	$101.90
Purchase #5	$40.89	13.852%	$46.5541	$46.55	$46.55	$46.60
Purchase #6	$102.69	5.858%	$108.7056	$108.71	$108.70	$108.70
Purchase #7	$169.44	9.565%	$185.6469	$185.65	$185.65	$185.60
7 purchase totals =	$527.27		$564.5527	$564.55	$564.55	$564.60