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	$232.79	5.673%	$245.9962	$246.00	$246.00	$246.00
Purchase #2	$172.93	5.597%	$182.6089	$182.61	$182.60	$182.60
Purchase #3	$145.71	6.385%	$155.0136	$155.01	$155.00	$155.00
Purchase #4	$93.46	8.625%	$101.5209	$101.52	$101.50	$101.50
Purchase #5	$68.73	5.321%	$72.3871	$72.39	$72.40	$72.40
Purchase #6	$143.39	6.286%	$152.4035	$152.40	$152.40	$152.40
Purchase #7	$139.75	11.636%	$156.0113	$156.01	$156.00	$156.00
7 purchase totals =	$996.76		$1,065.9415	$1,065.94	$1,065.90	$1,065.90