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	$63.54	4.428%	$66.3536	$66.35	$66.35	$66.40
Purchase #2	$115.62	13.320%	$131.0206	$131.02	$131.00	$131.00
Purchase #3	$181.55	6.827%	$193.9444	$193.94	$193.95	$193.90
Purchase #4	$165.50	13.292%	$187.4983	$187.50	$187.50	$187.50
Purchase #5	$103.78	7.746%	$111.8188	$111.82	$111.80	$111.80
Purchase #6	$77.39	6.428%	$82.3646	$82.36	$82.35	$82.40
Purchase #7	$225.64	7.401%	$242.3396	$242.34	$242.35	$242.30
7 purchase totals =	$933.02		$1,015.3399	$1,015.33	$1,015.30	$1,015.30