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	$211.29	7.834%	$227.8425	$227.84	$227.85	$227.80
Purchase #2	$155.86	5.473%	$164.3902	$164.39	$164.40	$164.40
Purchase #3	$237.52	7.329%	$254.9278	$254.93	$254.95	$254.90
Purchase #4	$55.89	5.848%	$59.1584	$59.16	$59.15	$59.20
Purchase #5	$107.43	8.821%	$116.9064	$116.91	$116.90	$116.90
Purchase #6	$23.69	9.611%	$25.9668	$25.97	$25.95	$26.00
Purchase #7	$59.32	9.290%	$64.8308	$64.83	$64.85	$64.80
7 purchase totals =	$851.00		$914.0229	$914.03	$914.05	$914.00