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	$137.55	5.702%	$145.3931	$145.39	$145.40	$145.40
Purchase #2	$196.98	13.548%	$223.6669	$223.67	$223.65	$223.70
Purchase #3	$129.35	7.830%	$139.4781	$139.48	$139.50	$139.50
Purchase #4	$246.49	6.438%	$262.359	$262.36	$262.35	$262.40
Purchase #5	$233.35	9.607%	$255.7679	$255.77	$255.75	$255.80
Purchase #6	$81.92	8.770%	$89.1044	$89.10	$89.10	$89.10
Purchase #7	$131.88	11.658%	$147.2546	$147.25	$147.25	$147.30
7 purchase totals =	$1,157.52		$1,263.0240	$1,263.02	$1,263.00	$1,263.20