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	$43.48	5.532%	$45.8853	$45.89	$45.90	$45.90
Purchase #2	$123.79	7.581%	$133.1745	$133.17	$133.15	$133.20
Purchase #3	$225.85	7.324%	$242.3913	$242.39	$242.40	$242.40
Purchase #4	$171.69	12.486%	$193.1272	$193.13	$193.15	$193.10
Purchase #5	$41.60	9.735%	$45.6498	$45.65	$45.65	$45.60
Purchase #6	$87.52	9.712%	$96.0199	$96.02	$96.00	$96.00
Purchase #7	$123.54	3.304%	$127.6218	$127.62	$127.60	$127.60
7 purchase totals =	$817.47		$883.8698	$883.87	$883.85	$883.80