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	$242.72	8.274%	$262.8027	$262.80	$262.80	$262.80
Purchase #2	$90.37	6.472%	$96.2187	$96.22	$96.20	$96.20
Purchase #3	$12.88	4.139%	$13.4131	$13.41	$13.40	$13.40
Purchase #4	$166.74	11.568%	$186.0285	$186.03	$186.05	$186.00
Purchase #5	$12.66	5.536%	$13.3609	$13.36	$13.35	$13.40
Purchase #6	$183.97	6.636%	$196.1782	$196.18	$196.20	$196.20
Purchase #7	$218.89	6.496%	$233.1091	$233.11	$233.10	$233.10
7 purchase totals =	$928.23		$1,001.1112	$1,001.11	$1,001.10	$1,001.10