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	$98.29	11.717%	$109.8066	$109.81	$109.80	$109.80
Purchase #2	$182.59	11.508%	$203.6025	$203.60	$203.60	$203.60
Purchase #3	$18.25	4.609%	$19.0911	$19.09	$19.10	$19.10
Purchase #4	$128.42	12.594%	$144.5932	$144.59	$144.60	$144.60
Purchase #5	$187.83	4.586%	$196.4439	$196.44	$196.45	$196.40
Purchase #6	$161.43	6.743%	$172.3152	$172.32	$172.30	$172.30
Purchase #7	$100.63	13.634%	$114.3499	$114.35	$114.35	$114.30
7 purchase totals =	$877.44		$960.2024	$960.20	$960.20	$960.10