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	$219.59	7.645%	$236.3777	$236.38	$236.40	$236.40
Purchase #2	$35.77	13.625%	$40.6437	$40.64	$40.65	$40.60
Purchase #3	$205.52	13.680%	$233.6351	$233.64	$233.65	$233.60
Purchase #4	$156.52	8.197%	$169.3499	$169.35	$169.35	$169.30
Purchase #5	$89.59	3.661%	$92.8699	$92.87	$92.85	$92.90
Purchase #6	$140.58	7.577%	$151.2317	$151.23	$151.25	$151.20
Purchase #7	$161.79	3.858%	$168.0319	$168.03	$168.05	$168.00
7 purchase totals =	$1,009.36		$1,092.1399	$1,092.14	$1,092.20	$1,092.00