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	$93.76	11.424%	$104.4711	$104.47	$104.45	$104.50
Purchase #2	$124.56	11.599%	$139.0077	$139.01	$139.00	$139.00
Purchase #3	$217.73	10.783%	$241.2078	$241.21	$241.20	$241.20
Purchase #4	$228.94	11.762%	$255.8679	$255.87	$255.85	$255.90
Purchase #5	$166.51	7.568%	$179.1115	$179.11	$179.10	$179.10
Purchase #6	$130.29	11.860%	$145.7424	$145.74	$145.75	$145.70
Purchase #7	$16.57	8.142%	$17.9191	$17.92	$17.90	$17.90
7 purchase totals =	$978.36		$1,083.3275	$1,083.33	$1,083.25	$1,083.30