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	$114.95	10.822%	$127.3899	$127.39	$127.40	$127.40
Purchase #2	$238.69	7.791%	$257.2863	$257.29	$257.30	$257.30
Purchase #3	$114.92	6.429%	$122.3082	$122.31	$122.30	$122.30
Purchase #4	$186.29	12.391%	$209.3732	$209.37	$209.35	$209.40
Purchase #5	$77.92	11.224%	$86.6657	$86.67	$86.65	$86.70
Purchase #6	$160.33	8.488%	$173.9388	$173.94	$173.95	$173.90
Purchase #7	$37.31	10.631%	$41.2764	$41.28	$41.30	$41.30
7 purchase totals =	$930.41		$1,018.2385	$1,018.25	$1,018.25	$1,018.30