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	$222.31	6.387%	$236.5089	$236.51	$236.50	$236.50
Purchase #2	$163.61	7.832%	$176.4239	$176.42	$176.40	$176.40
Purchase #3	$86.29	4.847%	$90.4725	$90.47	$90.45	$90.50
Purchase #4	$150.73	7.116%	$161.4559	$161.46	$161.45	$161.50
Purchase #5	$48.88	12.727%	$55.101	$55.10	$55.10	$55.10
Purchase #6	$242.42	10.550%	$267.9953	$268.00	$268.00	$268.00
Purchase #7	$31.36	13.662%	$35.6444	$35.64	$35.65	$35.60
7 purchase totals =	$945.60		$1,023.6019	$1,023.60	$1,023.55	$1,023.60