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	$70.44	10.790%	$78.0405	$78.04	$78.05	$78.00
Purchase #2	$190.53	4.746%	$199.5726	$199.57	$199.55	$199.60
Purchase #3	$99.79	3.676%	$103.4583	$103.46	$103.45	$103.50
Purchase #4	$21.50	3.316%	$22.2129	$22.21	$22.20	$22.20
Purchase #5	$21.52	9.774%	$23.6234	$23.62	$23.60	$23.60
Purchase #6	$197.36	13.433%	$223.8714	$223.87	$223.85	$223.90
Purchase #7	$250.71	4.524%	$262.0521	$262.05	$262.05	$262.10
7 purchase totals =	$851.85		$912.8312	$912.82	$912.75	$912.90