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	$148.29	11.453%	$165.2737	$165.27	$165.25	$165.30
Purchase #2	$53.49	7.452%	$57.4761	$57.48	$57.50	$57.50
Purchase #3	$126.67	7.709%	$136.435	$136.44	$136.45	$136.40
Purchase #4	$52.75	11.861%	$59.0067	$59.01	$59.00	$59.00
Purchase #5	$176.35	5.498%	$186.0457	$186.05	$186.05	$186.00
Purchase #6	$246.89	3.557%	$255.6719	$255.67	$255.65	$255.70
Purchase #7	$238.56	5.617%	$251.9599	$251.96	$251.95	$252.00
7 purchase totals =	$1,043.00		$1,111.8690	$1,111.88	$1,111.85	$1,111.90