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	$217.93	12.311%	$244.7594	$244.76	$244.75	$244.80
Purchase #2	$166.80	6.529%	$177.6904	$177.69	$177.70	$177.70
Purchase #3	$89.91	7.712%	$96.8439	$96.84	$96.85	$96.80
Purchase #4	$188.94	12.586%	$212.72	$212.72	$212.70	$212.70
Purchase #5	$153.47	11.544%	$171.1866	$171.19	$171.20	$171.20
Purchase #6	$64.52	10.819%	$71.5004	$71.50	$71.50	$71.50
Purchase #7	$39.93	9.697%	$43.802	$43.80	$43.80	$43.80
7 purchase totals =	$921.50		$1,018.5027	$1,018.50	$1,018.50	$1,018.50