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	$148.33	13.797%	$168.7951	$168.80	$168.80	$168.80
Purchase #2	$82.76	9.565%	$90.676	$90.68	$90.70	$90.70
Purchase #3	$100.41	8.249%	$108.6928	$108.69	$108.70	$108.70
Purchase #4	$250.85	9.376%	$274.3697	$274.37	$274.35	$274.40
Purchase #5	$148.34	9.338%	$162.192	$162.19	$162.20	$162.20
Purchase #6	$153.88	13.107%	$174.0491	$174.05	$174.05	$174.00
Purchase #7	$110.50	3.818%	$114.7189	$114.72	$114.70	$114.70
7 purchase totals =	$995.07		$1,093.4936	$1,093.50	$1,093.50	$1,093.50