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	$71.84	12.824%	$81.0528	$81.05	$81.05	$81.10
Purchase #2	$153.57	6.847%	$164.0849	$164.08	$164.10	$164.10
Purchase #3	$41.53	4.463%	$43.3835	$43.38	$43.40	$43.40
Purchase #4	$96.81	4.217%	$100.8925	$100.89	$100.90	$100.90
Purchase #5	$167.47	11.227%	$186.2719	$186.27	$186.25	$186.30
Purchase #6	$250.68	9.491%	$274.472	$274.47	$274.45	$274.50
Purchase #7	$149.98	12.855%	$169.2599	$169.26	$169.25	$169.30
7 purchase totals =	$931.88		$1,019.4175	$1,019.40	$1,019.40	$1,019.60