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	$181.56	10.481%	$200.5893	$200.59	$200.60	$200.60
Purchase #2	$173.60	13.234%	$196.5742	$196.57	$196.55	$196.60
Purchase #3	$79.77	6.739%	$85.1457	$85.15	$85.15	$85.10
Purchase #4	$231.59	8.466%	$251.1964	$251.20	$251.20	$251.20
Purchase #5	$143.60	6.721%	$153.2514	$153.25	$153.25	$153.30
Purchase #6	$186.36	13.680%	$211.854	$211.85	$211.85	$211.90
Purchase #7	$245.65	11.596%	$274.1356	$274.14	$274.15	$274.10
7 purchase totals =	$1,242.13		$1,372.7466	$1,372.75	$1,372.75	$1,372.80