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	$30.76	10.210%	$33.9006	$33.90	$33.90	$33.90
Purchase #2	$152.73	4.296%	$159.2913	$159.29	$159.30	$159.30
Purchase #3	$233.53	6.669%	$249.1041	$249.10	$249.10	$249.10
Purchase #4	$84.88	6.808%	$90.6586	$90.66	$90.65	$90.70
Purchase #5	$212.88	9.684%	$233.4953	$233.50	$233.50	$233.50
Purchase #6	$138.49	3.620%	$143.5033	$143.50	$143.50	$143.50
Purchase #7	$191.51	6.206%	$203.3951	$203.40	$203.40	$203.40
7 purchase totals =	$1,044.78		$1,113.3483	$1,113.35	$1,113.35	$1,113.40