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	$23.59	4.787%	$24.7193	$24.72	$24.70	$24.70
Purchase #2	$148.26	3.214%	$153.0251	$153.03	$153.05	$153.00
Purchase #3	$65.60	10.427%	$72.4401	$72.44	$72.45	$72.40
Purchase #4	$220.50	9.497%	$241.4409	$241.44	$241.45	$241.40
Purchase #5	$21.35	4.839%	$22.3831	$22.38	$22.40	$22.40
Purchase #6	$196.42	7.632%	$211.4108	$211.41	$211.40	$211.40
Purchase #7	$163.78	13.475%	$185.8494	$185.85	$185.85	$185.80
7 purchase totals =	$839.50		$911.2687	$911.27	$911.30	$911.10