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	$208.71	7.238%	$223.8164	$223.82	$223.80	$223.80
Purchase #2	$207.91	3.609%	$215.4135	$215.41	$215.40	$215.40
Purchase #3	$80.47	8.740%	$87.5031	$87.50	$87.50	$87.50
Purchase #4	$127.98	13.114%	$144.7633	$144.76	$144.75	$144.80
Purchase #5	$97.37	11.272%	$108.3455	$108.35	$108.35	$108.30
Purchase #6	$169.52	10.633%	$187.5451	$187.55	$187.55	$187.50
Purchase #7	$243.32	4.597%	$254.5054	$254.51	$254.50	$254.50
7 purchase totals =	$1,135.28		$1,221.8923	$1,221.90	$1,221.85	$1,221.80