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	$215.42	5.585%	$227.4512	$227.45	$227.45	$227.50
Purchase #2	$168.86	8.308%	$182.8889	$182.89	$182.90	$182.90
Purchase #3	$104.81	9.608%	$114.8801	$114.88	$114.90	$114.90
Purchase #4	$103.31	6.349%	$109.8692	$109.87	$109.85	$109.90
Purchase #5	$40.25	8.292%	$43.5875	$43.59	$43.60	$43.60
Purchase #6	$12.42	9.421%	$13.5901	$13.59	$13.60	$13.60
Purchase #7	$92.44	5.355%	$97.3902	$97.39	$97.40	$97.40
7 purchase totals =	$737.51		$789.6572	$789.66	$789.70	$789.80