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	$79.93	9.611%	$87.6121	$87.61	$87.60	$87.60
Purchase #2	$96.46	13.501%	$109.4831	$109.48	$109.50	$109.50
Purchase #3	$191.25	7.656%	$205.8921	$205.89	$205.90	$205.90
Purchase #4	$204.43	5.242%	$215.1462	$215.15	$215.15	$215.10
Purchase #5	$20.93	12.142%	$23.4713	$23.47	$23.45	$23.50
Purchase #6	$134.94	11.460%	$150.4041	$150.40	$150.40	$150.40
Purchase #7	$124.86	6.771%	$133.3143	$133.31	$133.30	$133.30
7 purchase totals =	$852.80		$925.3232	$925.31	$925.30	$925.30