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	$53.37	11.161%	$59.3266	$59.33	$59.35	$59.30
Purchase #2	$135.30	6.783%	$144.4774	$144.48	$144.50	$144.50
Purchase #3	$235.59	10.375%	$260.0325	$260.03	$260.05	$260.00
Purchase #4	$63.43	7.801%	$68.3782	$68.38	$68.40	$68.40
Purchase #5	$186.95	5.829%	$197.8473	$197.85	$197.85	$197.80
Purchase #6	$153.73	11.557%	$171.4966	$171.50	$171.50	$171.50
Purchase #7	$133.49	11.176%	$148.4088	$148.41	$148.40	$148.40
7 purchase totals =	$961.86		$1,049.9674	$1,049.98	$1,050.05	$1,049.90