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	$96.25	13.532%	$109.2746	$109.27	$109.25	$109.30
Purchase #2	$23.97	4.726%	$25.1028	$25.10	$25.10	$25.10
Purchase #3	$23.74	4.389%	$24.7819	$24.78	$24.80	$24.80
Purchase #4	$228.27	6.410%	$242.9021	$242.90	$242.90	$242.90
Purchase #5	$91.92	7.718%	$99.0144	$99.01	$99.00	$99.00
Purchase #6	$81.99	5.508%	$86.506	$86.51	$86.50	$86.50
Purchase #7	$179.33	11.741%	$200.3851	$200.39	$200.40	$200.40
7 purchase totals =	$725.47		$787.9669	$787.96	$787.95	$788.00