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	$196.37	5.675%	$207.514	$207.51	$207.50	$207.50
Purchase #2	$55.61	10.835%	$61.6353	$61.64	$61.65	$61.60
Purchase #3	$47.41	7.637%	$51.0307	$51.03	$51.05	$51.00
Purchase #4	$196.82	8.610%	$213.7662	$213.77	$213.75	$213.80
Purchase #5	$82.34	10.380%	$90.8869	$90.89	$90.90	$90.90
Purchase #6	$107.27	7.405%	$115.2133	$115.21	$115.20	$115.20
Purchase #7	$49.94	9.223%	$54.546	$54.55	$54.55	$54.50
7 purchase totals =	$735.76		$794.5924	$794.60	$794.60	$794.50