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	$126.75	4.233%	$132.1153	$132.12	$132.10	$132.10
Purchase #2	$143.91	4.565%	$150.4795	$150.48	$150.50	$150.50
Purchase #3	$181.87	5.143%	$191.2236	$191.22	$191.20	$191.20
Purchase #4	$158.31	5.557%	$167.1073	$167.11	$167.10	$167.10
Purchase #5	$150.63	12.596%	$169.6034	$169.60	$169.60	$169.60
Purchase #6	$22.93	8.396%	$24.8552	$24.86	$24.85	$24.90
Purchase #7	$81.50	11.212%	$90.6378	$90.64	$90.65	$90.60
7 purchase totals =	$865.90		$926.0221	$926.03	$926.00	$926.00