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	$41.35	6.657%	$44.1027	$44.10	$44.10	$44.10
Purchase #2	$133.76	6.834%	$142.9012	$142.90	$142.90	$142.90
Purchase #3	$127.93	10.110%	$140.8637	$140.86	$140.85	$140.90
Purchase #4	$94.57	10.360%	$104.3675	$104.37	$104.35	$104.40
Purchase #5	$107.80	11.706%	$120.4191	$120.42	$120.40	$120.40
Purchase #6	$140.89	7.501%	$151.4582	$151.46	$151.45	$151.50
Purchase #7	$20.38	3.442%	$21.0815	$21.08	$21.10	$21.10
7 purchase totals =	$666.68		$725.1939	$725.19	$725.15	$725.30