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	$117.84	11.359%	$131.2254	$131.23	$131.25	$131.20
Purchase #2	$182.45	12.541%	$205.3311	$205.33	$205.35	$205.30
Purchase #3	$151.60	12.847%	$171.0761	$171.08	$171.10	$171.10
Purchase #4	$71.50	7.152%	$76.6137	$76.61	$76.60	$76.60
Purchase #5	$151.45	9.275%	$165.497	$165.50	$165.50	$165.50
Purchase #6	$127.93	13.521%	$145.2274	$145.23	$145.25	$145.20
Purchase #7	$214.83	9.736%	$235.7458	$235.75	$235.75	$235.70
7 purchase totals =	$1,017.60		$1,130.7165	$1,130.73	$1,130.80	$1,130.60