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	$188.39	4.807%	$197.4459	$197.45	$197.45	$197.40
Purchase #2	$112.39	13.462%	$127.5199	$127.52	$127.50	$127.50
Purchase #3	$183.72	4.417%	$191.8349	$191.83	$191.85	$191.80
Purchase #4	$9.39	11.453%	$10.4654	$10.47	$10.45	$10.50
Purchase #5	$80.63	3.334%	$83.3182	$83.32	$83.30	$83.30
Purchase #6	$176.42	12.648%	$198.7336	$198.73	$198.75	$198.70
Purchase #7	$38.55	12.756%	$43.4674	$43.47	$43.45	$43.50
7 purchase totals =	$789.49		$852.7853	$852.79	$852.75	$852.70