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	$213.33	4.374%	$222.6611	$222.66	$222.65	$222.70
Purchase #2	$75.81	8.565%	$82.3031	$82.30	$82.30	$82.30
Purchase #3	$250.33	11.317%	$278.6598	$278.66	$278.65	$278.70
Purchase #4	$161.49	12.609%	$181.8523	$181.85	$181.85	$181.90
Purchase #5	$87.34	5.200%	$91.8817	$91.88	$91.90	$91.90
Purchase #6	$34.32	3.256%	$35.4375	$35.44	$35.45	$35.40
Purchase #7	$127.69	7.867%	$137.7354	$137.74	$137.75	$137.70
7 purchase totals =	$950.31		$1,030.5309	$1,030.53	$1,030.55	$1,030.60