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	$39.76	13.183%	$45.0016	$45.00	$45.00	$45.00
Purchase #2	$223.36	4.701%	$233.8602	$233.86	$233.85	$233.90
Purchase #3	$224.85	7.649%	$242.0488	$242.05	$242.05	$242.00
Purchase #4	$84.86	11.454%	$94.5799	$94.58	$94.60	$94.60
Purchase #5	$249.31	12.851%	$281.3488	$281.35	$281.35	$281.30
Purchase #6	$155.59	9.175%	$169.8654	$169.87	$169.85	$169.90
Purchase #7	$24.60	12.396%	$27.6494	$27.65	$27.65	$27.60
7 purchase totals =	$1,002.33		$1,094.3541	$1,094.36	$1,094.35	$1,094.30