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	$215.37	11.537%	$240.2172	$240.22	$240.20	$240.20
Purchase #2	$204.41	5.476%	$215.6035	$215.60	$215.60	$215.60
Purchase #3	$54.94	9.833%	$60.3423	$60.34	$60.35	$60.30
Purchase #4	$29.61	11.233%	$32.9361	$32.94	$32.95	$32.90
Purchase #5	$198.52	6.653%	$211.7275	$211.73	$211.75	$211.70
Purchase #6	$119.33	3.323%	$123.2953	$123.30	$123.30	$123.30
Purchase #7	$186.92	10.692%	$206.9055	$206.91	$206.90	$206.90
7 purchase totals =	$1,009.10		$1,091.0274	$1,091.04	$1,091.05	$1,090.90