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	$59.67	3.263%	$61.617	$61.62	$61.60	$61.60
Purchase #2	$201.41	8.449%	$218.4271	$218.43	$218.45	$218.40
Purchase #3	$159.61	4.805%	$167.2793	$167.28	$167.30	$167.30
Purchase #4	$216.76	8.388%	$234.9418	$234.94	$234.95	$234.90
Purchase #5	$62.70	6.206%	$66.5912	$66.59	$66.60	$66.60
Purchase #6	$238.74	12.107%	$267.6443	$267.64	$267.65	$267.60
Purchase #7	$84.43	9.569%	$92.5091	$92.51	$92.50	$92.50
7 purchase totals =	$1,023.32		$1,109.0098	$1,109.01	$1,109.05	$1,108.90