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	$219.30	4.179%	$228.4645	$228.46	$228.45	$228.50
Purchase #2	$242.50	13.643%	$275.5843	$275.58	$275.60	$275.60
Purchase #3	$82.73	3.155%	$85.3401	$85.34	$85.35	$85.30
Purchase #4	$67.34	7.431%	$72.344	$72.34	$72.35	$72.30
Purchase #5	$107.95	12.645%	$121.6003	$121.60	$121.60	$121.60
Purchase #6	$52.96	5.444%	$55.8431	$55.84	$55.85	$55.80
Purchase #7	$27.30	9.165%	$29.802	$29.80	$29.80	$29.80
7 purchase totals =	$800.08		$868.9783	$868.96	$869.00	$868.90