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	$88.45	13.740%	$100.603	$100.60	$100.60	$100.60
Purchase #2	$224.39	13.435%	$254.5368	$254.54	$254.55	$254.50
Purchase #3	$249.89	6.632%	$266.4627	$266.46	$266.45	$266.50
Purchase #4	$79.65	5.740%	$84.2219	$84.22	$84.20	$84.20
Purchase #5	$119.43	12.494%	$134.3516	$134.35	$134.35	$134.40
Purchase #6	$81.31	6.389%	$86.5049	$86.50	$86.50	$86.50
Purchase #7	$228.46	11.691%	$255.1693	$255.17	$255.15	$255.20
7 purchase totals =	$1,071.58		$1,181.8502	$1,181.84	$1,181.80	$1,181.90