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	$114.90	11.419%	$128.0204	$128.02	$128.00	$128.00
Purchase #2	$50.36	4.289%	$52.5199	$52.52	$52.50	$52.50
Purchase #3	$197.39	4.711%	$206.689	$206.69	$206.70	$206.70
Purchase #4	$102.95	8.396%	$111.5937	$111.59	$111.60	$111.60
Purchase #5	$88.42	4.571%	$92.4617	$92.46	$92.45	$92.50
Purchase #6	$179.84	3.405%	$185.9636	$185.96	$185.95	$186.00
Purchase #7	$7.96	3.307%	$8.2232	$8.22	$8.20	$8.20
7 purchase totals =	$741.82		$785.4715	$785.46	$785.40	$785.50