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	$213.43	6.478%	$227.256	$227.26	$227.25	$227.30
Purchase #2	$145.54	13.816%	$165.6478	$165.65	$165.65	$165.60
Purchase #3	$54.88	9.113%	$59.8812	$59.88	$59.90	$59.90
Purchase #4	$70.80	3.482%	$73.2653	$73.27	$73.25	$73.30
Purchase #5	$27.54	3.180%	$28.4158	$28.42	$28.40	$28.40
Purchase #6	$183.42	13.660%	$208.4752	$208.48	$208.50	$208.50
Purchase #7	$238.42	5.205%	$250.8298	$250.83	$250.85	$250.80
7 purchase totals =	$934.03		$1,013.7711	$1,013.79	$1,013.80	$1,013.80