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	$182.88	8.755%	$198.8911	$198.89	$198.90	$198.90
Purchase #2	$98.60	10.592%	$109.0437	$109.04	$109.05	$109.00
Purchase #3	$41.27	3.443%	$42.6909	$42.69	$42.70	$42.70
Purchase #4	$150.93	11.339%	$168.044	$168.04	$168.05	$168.00
Purchase #5	$161.36	9.254%	$176.2923	$176.29	$176.30	$176.30
Purchase #6	$81.54	10.730%	$90.2892	$90.29	$90.30	$90.30
Purchase #7	$120.81	13.269%	$136.8403	$136.84	$136.85	$136.80
7 purchase totals =	$837.39		$922.0915	$922.08	$922.15	$922.00