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	$85.93	12.243%	$96.4504	$96.45	$96.45	$96.50
Purchase #2	$250.43	12.119%	$280.7796	$280.78	$280.80	$280.80
Purchase #3	$208.30	4.759%	$218.213	$218.21	$218.20	$218.20
Purchase #4	$128.41	10.751%	$142.2154	$142.22	$142.20	$142.20
Purchase #5	$136.82	6.345%	$145.5012	$145.50	$145.50	$145.50
Purchase #6	$143.65	11.600%	$160.3134	$160.31	$160.30	$160.30
Purchase #7	$120.34	9.502%	$131.7747	$131.77	$131.75	$131.80
7 purchase totals =	$1,073.88		$1,175.2477	$1,175.24	$1,175.20	$1,175.30