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	$229.36	5.325%	$241.5734	$241.57	$241.55	$241.60
Purchase #2	$21.38	9.839%	$23.4836	$23.48	$23.50	$23.50
Purchase #3	$79.48	9.374%	$86.9305	$86.93	$86.95	$86.90
Purchase #4	$29.57	8.168%	$31.9853	$31.99	$32.00	$32.00
Purchase #5	$60.51	11.445%	$67.4354	$67.44	$67.45	$67.40
Purchase #6	$230.71	10.709%	$255.4167	$255.42	$255.40	$255.40
Purchase #7	$115.97	10.223%	$127.8256	$127.83	$127.85	$127.80
7 purchase totals =	$766.98		$834.6505	$834.66	$834.70	$834.60