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	$103.72	9.702%	$113.7829	$113.78	$113.80	$113.80
Purchase #2	$115.80	10.103%	$127.4993	$127.50	$127.50	$127.50
Purchase #3	$45.56	5.269%	$47.9606	$47.96	$47.95	$48.00
Purchase #4	$224.72	11.453%	$250.4572	$250.46	$250.45	$250.50
Purchase #5	$98.54	13.259%	$111.6054	$111.61	$111.60	$111.60
Purchase #6	$225.77	6.434%	$240.296	$240.30	$240.30	$240.30
Purchase #7	$38.72	12.817%	$43.6827	$43.68	$43.70	$43.70
7 purchase totals =	$852.83		$935.2841	$935.29	$935.30	$935.40