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	$61.66	5.734%	$65.1956	$65.20	$65.20	$65.20
Purchase #2	$43.84	3.834%	$45.5208	$45.52	$45.50	$45.50
Purchase #3	$250.95	11.237%	$279.1493	$279.15	$279.15	$279.10
Purchase #4	$32.95	13.474%	$37.3897	$37.39	$37.40	$37.40
Purchase #5	$201.69	11.254%	$224.3882	$224.39	$224.40	$224.40
Purchase #6	$167.86	7.709%	$180.8003	$180.80	$180.80	$180.80
Purchase #7	$239.39	4.373%	$249.8585	$249.86	$249.85	$249.90
7 purchase totals =	$998.34		$1,082.3024	$1,082.31	$1,082.30	$1,082.30