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	$229.89	4.582%	$240.4236	$240.42	$240.40	$240.40
Purchase #2	$139.89	9.176%	$152.7263	$152.73	$152.75	$152.70
Purchase #3	$7.56	5.127%	$7.9476	$7.95	$7.95	$7.90
Purchase #4	$107.77	10.167%	$118.727	$118.73	$118.75	$118.70
Purchase #5	$199.33	11.452%	$222.1573	$222.16	$222.15	$222.20
Purchase #6	$186.83	7.851%	$201.498	$201.50	$201.50	$201.50
Purchase #7	$239.47	3.569%	$248.0167	$248.02	$248.00	$248.00
7 purchase totals =	$1,110.74		$1,191.4965	$1,191.51	$1,191.50	$1,191.40