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	$158.41	8.789%	$172.3327	$172.33	$172.35	$172.30
Purchase #2	$120.58	9.487%	$132.0194	$132.02	$132.00	$132.00
Purchase #3	$92.47	11.851%	$103.4286	$103.43	$103.45	$103.40
Purchase #4	$101.71	7.846%	$109.6902	$109.69	$109.70	$109.70
Purchase #5	$216.37	12.303%	$242.99	$242.99	$243.00	$243.00
Purchase #6	$127.36	7.539%	$136.9617	$136.96	$136.95	$137.00
Purchase #7	$172.95	9.499%	$189.3785	$189.38	$189.40	$189.40
7 purchase totals =	$989.85		$1,086.8011	$1,086.80	$1,086.85	$1,086.80