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	$173.69	7.769%	$187.184	$187.18	$187.20	$187.20
Purchase #2	$187.27	13.687%	$212.9016	$212.90	$212.90	$212.90
Purchase #3	$159.69	6.611%	$170.2471	$170.25	$170.25	$170.20
Purchase #4	$122.48	7.404%	$131.5484	$131.55	$131.55	$131.50
Purchase #5	$85.56	11.601%	$95.4858	$95.49	$95.50	$95.50
Purchase #6	$127.59	13.587%	$144.9257	$144.93	$144.95	$144.90
Purchase #7	$187.64	8.425%	$203.4487	$203.45	$203.45	$203.40
7 purchase totals =	$1,043.92		$1,145.7413	$1,145.75	$1,145.80	$1,145.60