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	$42.59	9.158%	$46.4904	$46.49	$46.50	$46.50
Purchase #2	$175.39	13.696%	$199.4114	$199.41	$199.40	$199.40
Purchase #3	$216.96	13.820%	$246.9439	$246.94	$246.95	$246.90
Purchase #4	$72.69	8.113%	$78.5873	$78.59	$78.60	$78.60
Purchase #5	$231.60	7.719%	$249.4772	$249.48	$249.50	$249.50
Purchase #6	$181.33	3.491%	$187.6602	$187.66	$187.65	$187.70
Purchase #7	$80.49	6.268%	$85.5351	$85.54	$85.55	$85.50
7 purchase totals =	$1,001.05		$1,094.1055	$1,094.11	$1,094.15	$1,094.10