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	$106.76	4.324%	$111.3763	$111.38	$111.40	$111.40
Purchase #2	$33.25	7.478%	$35.7364	$35.74	$35.75	$35.70
Purchase #3	$107.75	12.863%	$121.6099	$121.61	$121.60	$121.60
Purchase #4	$173.83	9.219%	$189.8554	$189.86	$189.85	$189.90
Purchase #5	$167.97	6.709%	$179.2391	$179.24	$179.25	$179.20
Purchase #6	$231.45	7.811%	$249.5286	$249.53	$249.55	$249.50
Purchase #7	$24.41	12.663%	$27.501	$27.50	$27.50	$27.50
7 purchase totals =	$845.42		$914.8467	$914.86	$914.90	$914.80