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	$43.26	8.309%	$46.8545	$46.85	$46.85	$46.90
Purchase #2	$28.30	11.443%	$31.5384	$31.54	$31.55	$31.50
Purchase #3	$239.83	3.520%	$248.272	$248.27	$248.25	$248.30
Purchase #4	$179.46	11.488%	$200.0764	$200.08	$200.10	$200.10
Purchase #5	$201.70	4.872%	$211.5268	$211.53	$211.55	$211.50
Purchase #6	$229.49	12.607%	$258.4218	$258.42	$258.40	$258.40
Purchase #7	$63.39	4.181%	$66.0403	$66.04	$66.05	$66.00
7 purchase totals =	$985.43		$1,062.7302	$1,062.73	$1,062.75	$1,062.70