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	$233.79	3.392%	$241.7202	$241.72	$241.70	$241.70
Purchase #2	$144.62	10.248%	$159.4407	$159.44	$159.45	$159.40
Purchase #3	$73.92	12.864%	$83.4291	$83.43	$83.45	$83.40
Purchase #4	$129.38	9.495%	$141.6646	$141.66	$141.65	$141.70
Purchase #5	$168.86	13.525%	$191.6983	$191.70	$191.70	$191.70
Purchase #6	$115.64	11.411%	$128.8357	$128.84	$128.85	$128.80
Purchase #7	$67.56	3.774%	$70.1097	$70.11	$70.10	$70.10
7 purchase totals =	$933.77		$1,016.8983	$1,016.90	$1,016.90	$1,016.80