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	$200.47	11.278%	$223.079	$223.08	$223.10	$223.10
Purchase #2	$237.75	13.161%	$269.0403	$269.04	$269.05	$269.00
Purchase #3	$159.83	4.149%	$166.4613	$166.46	$166.45	$166.50
Purchase #4	$43.89	9.179%	$47.9187	$47.92	$47.90	$47.90
Purchase #5	$105.96	7.607%	$114.0204	$114.02	$114.00	$114.00
Purchase #6	$250.56	11.444%	$279.2341	$279.23	$279.25	$279.20
Purchase #7	$47.96	9.131%	$52.3392	$52.34	$52.35	$52.30
7 purchase totals =	$1,046.42		$1,152.0930	$1,152.09	$1,152.10	$1,152.00