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	$101.27	3.324%	$104.6362	$104.64	$104.65	$104.60
Purchase #2	$19.79	10.374%	$21.843	$21.84	$21.85	$21.80
Purchase #3	$98.41	3.458%	$101.813	$101.81	$101.80	$101.80
Purchase #4	$82.59	7.590%	$88.8586	$88.86	$88.85	$88.90
Purchase #5	$244.61	4.849%	$256.4711	$256.47	$256.45	$256.50
Purchase #6	$190.59	7.582%	$205.0405	$205.04	$205.05	$205.00
Purchase #7	$92.56	7.192%	$99.2169	$99.22	$99.20	$99.20
7 purchase totals =	$829.82		$877.8793	$877.88	$877.85	$877.80