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	$220.44	9.471%	$241.3179	$241.32	$241.30	$241.30
Purchase #2	$174.85	4.381%	$182.5102	$182.51	$182.50	$182.50
Purchase #3	$6.90	5.806%	$7.3006	$7.30	$7.30	$7.30
Purchase #4	$129.38	12.580%	$145.656	$145.66	$145.65	$145.70
Purchase #5	$154.78	6.632%	$165.045	$165.05	$165.05	$165.00
Purchase #6	$200.41	4.447%	$209.3222	$209.32	$209.30	$209.30
Purchase #7	$84.27	4.780%	$88.2981	$88.30	$88.30	$88.30
7 purchase totals =	$971.03		$1,039.4500	$1,039.46	$1,039.40	$1,039.40