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	$151.82	8.368%	$164.5243	$164.52	$164.50	$164.50
Purchase #2	$221.82	3.547%	$229.688	$229.69	$229.70	$229.70
Purchase #3	$134.55	13.400%	$152.5797	$152.58	$152.60	$152.60
Purchase #4	$189.78	6.374%	$201.8766	$201.88	$201.90	$201.90
Purchase #5	$171.84	7.155%	$184.1352	$184.14	$184.15	$184.10
Purchase #6	$108.89	8.470%	$118.113	$118.11	$118.10	$118.10
Purchase #7	$43.55	7.664%	$46.8877	$46.89	$46.90	$46.90
7 purchase totals =	$1,022.25		$1,097.8045	$1,097.81	$1,097.85	$1,097.80