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	$10.37	11.676%	$11.5808	$11.58	$11.60	$11.60
Purchase #2	$186.55	5.356%	$196.5416	$196.54	$196.55	$196.50
Purchase #3	$245.50	9.132%	$267.9191	$267.92	$267.90	$267.90
Purchase #4	$125.76	13.865%	$143.1966	$143.20	$143.20	$143.20
Purchase #5	$33.30	12.226%	$37.3713	$37.37	$37.35	$37.40
Purchase #6	$123.72	4.398%	$129.1612	$129.16	$129.15	$129.20
Purchase #7	$237.35	10.766%	$262.9031	$262.90	$262.90	$262.90
7 purchase totals =	$962.55		$1,048.6737	$1,048.67	$1,048.65	$1,048.70